Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

853-2427 29875

DESCRIPTION

The Philips P87CL5xX2 is a high-performance static 80C51 design
fabricated with Philips high-density CMOS technology with operation
from 1.8 V to 3.3 V.

The P87CL5xX2 ROMless devices contain a 256

8 RAM, 32 I/O

lines, three 16-bit counter/timers, a six-source, four-priority level
nested interrupt structure, a serial I/O port for either multi-processor
communications, I/O expansion or full duplex UART, and on-chip
oscillator and clock circuits.

In addition, the device is a low power static design which offers a
wide range of operating frequencies down to zero. Two software
selectable modes of power reduction -- idle mode and power-down
mode -- are available. The idle mode freezes the CPU while
allowing the RAM, time rs, serial port, and interrupt system to
continue functioning. The power-down mode saves the RAM
contents but freezes the oscillator, causing all other chip functions to
be inoperative. Since the design is static, the clock can be stopped
without loss of user data and then the execution resumed from the
point the clock was stopped.

FEATURES

8051 Central Processing Unit

TSSOP or LQFP packages

256

8 RAM

Three 16-bit counter/timers

Boolean processor

Full static operation

Low voltage (1.8 V to 3.3 V@ 12 MHz) operation (12-clock

mode)

Memory addressing capability

64k ROM and 64k RAM

Power control modes:

Clock can be stopped and resumed

Idle mode

Power-down mode

CMOS and TTL compatible

Two speed ranges at V

= 3.3 V

0 to 16 MHz (6-clock mode)

0 to 33 MHz (12-clock mode)

Dual Data Pointers

Four priority interrupt levels

Six interrupt sources

Four 8-bit I/O ports

Fullduplex enhanced UART

Framing error detection

Automatic address recognition

Programmable clock out

Asynchronous port reset

Low EMI (inhibit ALE)

Wake-up from Power Down by an external interrupt

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

LOGIC SYMBOL

POR

ADDRESS AND

DATA BUS

ADDRESS BUS

T2EX

RxD

TxD

INT0

INT1

SECONDAR

FUNCTIONS

RST

EA/V

PSEN

ALE/PROG

XTAL1

XTAL2

SU01724

NOTE:
1. INT0/P3.2 and T1/P3.5 are absent in the TSSOP38 package.

LOW PROFILE QUAD FLAT PACK
PIN FUNCTIONS

SU01487

LQFP

Pin

Function

P1.5

P1.6

P1.7

RST

P3.0/RxD

NIC*

P3.1/TxD

P3.2/INT0

P3.3/INT1

P3.4/T0

P3.5/T1

P3.6/WR

P3.7/RD

XTAL2

XTAL1

Pin

Function

NIC*

P2.0/A8

P2.1/A9

P2.2/A10

P2.3/A11

P2.4/A12

P2.5/A13

P2.6/A14

P2.7/A15

PSEN

ALE

NIC*

EA/V

P0.7/AD7

Pin

Function

P0.6/AD6

P0.5/AD5

P0.4/AD4

P0.3/AD3

P0.2/AD2

P0.1/AD1

P0.0/AD0

NIC*

P1.0/T2

P1.1/T2EX

P1.2

P1.3

P1.4

* NO INTERNAL CONNECTION

PLASTIC THIN SHRINK SMALL OUTLINE PACK
PIN FUNCTIONS

su01725

Pin

Function

P3.0/RxD

P3.1/TxD

P3.3/INT1

P3.4/T0

P3.6/WR

P3.7/RD

XTAL2

XTAL1

P2.0/A8

P2.1/A9

P2.2/A10

P2.3/A11

Pin

Function

P2.4/A12

P2.5/A13

P2.6/A14

P2.7/A15

PSEN

ALE/PROG

EA/V

P0.7/AD7

P0.6/AD6

P0.5/AD5

P0.4/AD4

P0.3/AD3

P0.2/AD2

Pin

Function

P0.1/AD1

P0.0/AD0

P1.0/T2

P1.1/T2EX

P1.2

P1.3

P1.4

P1.5

P1.6

P1.7

RST

TSSOP

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

PIN DESCRIPTIONS

PIN NUMBER

MNEMONIC

LQFP

TSSOP

TYPE

NAME AND FUNCTION

Ground: 0 V reference.

Power Supply: This is the power supply voltage for normal, idle, and power-down operation.

P0.00.7

3730

2821

I/O

Port 0: Port 0 is an open-drain, bidirectional I/O port with Schmitt trigger inputs. Port 0 pins
that have 1s written to them float and can be used as high-impedance inputs. Port 0 is also
the multiplexed low-order address and data bus during accesses to external program and
data memory. In this application, it uses strong internal pull-ups when emitting 1s.

P1.0P1.7

4044,

3037

I/O

Port 1: Port 1 is an 8-bit bidirectional I/O port with internal pull-ups and Schmitt trigger
inputs. Port 1 pins that have 1s written to them are pulled high by the internal pull-ups and
can be used as inputs. As inputs, port 1 pins that are externally pulled low will source
current because of the internal pull-ups. (See DC Electrical Characteristics: I

). Alternate

functions for Port 1 include:

I/O

T2 (P1.0):

Timer/Counter 2 external count input/clockout (see Programmable Clock-Out)

T2EX (P1.1): Timer/Counter 2 Reload/Capture/Direction control

P2.0P2.7

1825

1017

I/O

Port 2: Port 2 is an 8-bit bidirectional I/O port with internal pull-ups and Schmitt trigger
inputs. Port 2 pins that have 1s written to them are pulled high by the internal pull-ups and
can be used as inputs. As inputs, port 2 pins that are externally being pulled low will source
current because of the internal pull-ups. (See DC Electrical Characteristics: I

). Port 2 emits

the high-order address byte during fetches from external program memory and during
accesses to external data memory that use 16-bit addresses (MOVX @DPTR). In this
application, it uses strong internal pull-ups when emitting 1s. During accesses to external
data memory that use 8-bit addresses (MOV @Ri), port 2 emits the contents of the P2
special function register.

P3.0P3.7

713

I/O

Port 3: Port 3 is an 8-bit bidirectional I/O port with internal pull-ups and Schmitt trigger
inputs. Port 3 pins that have 1s written to them are pulled high by the internal pull-ups and
can be used as inputs. As inputs, port 3 pins that are externally being pulled low will source
current because of the pull-ups. (See DC Electrical Characteristics: I

). Port 3 also serves

the special features of the 80C51 family, as listed below:

RxD (P3.0): Serial input port

TxD (P3.1): Serial output port

INT0 (P3.2): External interrupt

INT1 (P3.3): External interrupt

T0 (P3.4): Timer 0 external input

T1 (P3.5): Timer 1 external input

WR (P3.6): External data memory write strobe

RD (P3.7): External data memory read strobe

RST

Reset: A high on this pin for two machine cycles while the oscillator is running, resets the
device. An internal diffused resistor to V

permits a power-on reset using only an external

capacitor to V

ALE

Address Latch Enable: Output pulse for latching the low byte of the address during an
access to external memory. In normal operation, ALE is emitted at a constant rate of 1/6 the
oscillator frequency, and can be used for external timing or clocking. Note that one ALE
pulse is skipped during each access to external data memory. ALE can be disabled by
setting SFR auxiliary.0. With this bit set, ALE will be active only during a MOVX instruction.

PSEN

Program Store Enable: The read strobe to external program memory. When the
P87CL5xX2 is executing code from the external program memory, PSEN is activated twice
each machine cycle, except that two PSEN activations are skipped during each access to
external data memory. PSEN is not activated during fetches from internal program memory.

EA/V

External Access Enable/Programming Supply Voltage: EA must be externally held low
to enable the device to fetch code from external program memory locations 0000H to
0FFFH.

XTAL1

Crystal 1: Input to the inverting oscillator amplifier and input to the internal clock generator
circuits.

XTAL2

Crystal 2: Output from the inverting oscillator amplifier.

NOTE:
To avoid "latch-up" effect at power-on, the voltage on any pin at any time must not be higher than V

+ 0.5 V or V

0.5 V, respectively.

1. Absent in the TSSOP38 package.

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

Table 1.

P87CL5xX2 Special Function Registers

SYMBOL

DESCRIPTION

DIRECT

ADDRESS

BIT ADDRESS, SYMBOL, OR ALTERNATIVE PORT FUNCTION

MSB

LSB

RESET
VALUE

ACC*

Accumulator

E0H

00H

AUXR#

Auxiliary

8EH

xxxxxxx0B

AUXR1#

Auxiliary 1

A2H

WUPD

DPS

xxx000x0B

B register

F0H

00H

CKCON

Clock Control Register

8FH

xxx00000B

DPTR:

Data Pointer (2 bytes)

DPH

Data Pointer High

83H

00H

DPL

Data Pointer Low

82H

00H

IE*

Interrupt Enable

A8H

ET2

ET1

EX1

ET0

EX0

0x000000B

IP*

Interrupt Priority

B8H

PT2

PT1

PX1

PT0

PX0

xx000000B

IPH#

Interrupt Priority High

B7H

PT2H

PSH

PT1H

PX1H

PT0H

PX0H

xx000000B

P0*

Port 0

80H

AD7

AD6

AD5

AD4

AD3

AD2

AD1

AD0

FFH

P1*

Port 1

90H

T2EX

FFH

P2*

Port 2

A0H

AD15

AD14

AD13

AD12

AD11

AD10

AD9

AD8

FFH

P3*

Port 3

B0H

INT1

INT0

TxD

RxD

FFH

PCON#

Power Control

87H

SMOD1

SMOD0

POF

GF1

GF0

IDL

00xx0000B

PSW*

Program Status Word

D0H

RS1

RS0

000000x0B

RACAP2H

Timer 2 Capture High

CBH

00H

RACAP2L

Timer 2 Capture Low

CAH

00H

SADDR#

Slave Address

A9H

00H

SADEN#

Slave Address Mask

B9H

00H

SBUF

Serial Data Buffer

99H

xxxxxxxxB

SCON*

Serial Control

98H

SM0/FE

SM1

SM2

REN

TB8

RB8

00H

Stack Pointer

81H

07H

TCON*

Timer Control

88H

TF1

TR1

TF0

TR0

IE1

IT1

IE0

IT0

00H

T2CON*

Timer 2 Control

C8H

TF2

EXF2

RCLK

TCLK

EXEN2

TR2

C/T2

CP/RL2

00H

T2MOD#

Timer 2 Mode Control

C9H

T2OE

DCEN

xxxxxx00B

TH0

Timer High 0

8CH

00H

TH1

Timer High 1

8DH

00H

TH2#

Timer High 2

CDH

00H

TL0

Timer Low 0

8AH

00H

TL1

Timer Low 1

8BH

00H

TL2#

Timer Low 2

CCH

00H

TMOD

Timer Mode

89H

GATE

C/T

GATE

C/T

00H

NOTE:
Unused register bits that are not defined should not be set by the user's program. If violated, the device could function incorrectly.
*

SFRs are bit addressable.

SFRs are modified from or added to the 80C51 SFRs.

Reserved bits.

1. Reset value depends on reset source.

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

OSCILLATOR CHARACTERISTICS

XTAL1 and XTAL2 are the input and output, respectively, of an
inverting amplifier. The pins can be configured for use as an on-chip
oscillator, as shown in the logic symbol.

To drive the device from an external clock source, XTAL1 should be
driven while XTAL2 is left unconnected. There are no requirements
on the duty cycle of the external clock signal, because the input to
the internal clock circuitry is through a divide-by-two flip-flop.
However, minimum and maximum high and low times specified in
the data sheet must be observed.

Clock Control Register (CKCON)

This device provides control of the 6-clock/12-clock mode by an
SFR bit (bit X2 in register CKCON). When X2 is 0, 12-clock mode is
activated. By setting this bit to 1, the system is switching to 6-clock
mode. Having this option implemented as SFR bit, it can be
accessed anytime and changed to either value. Changing X2 from 0
to 1 will result in executing user code at twice the speed, since all
system time intervals will be divided by 2. Changing back from
6-clock to 12-clock mode will slow down running code by a factor of
2.

Reset

A reset is accomplished by holding the RST pin high for at least two
machine cycles (24 oscillator periods), while the oscillator is running.
To insure a good power-up reset, the RST pin must be high long
enough to allow the oscillator time to start up (normally a few
milliseconds) plus two machine cycles.

Stop Clock Mode

The static design enables the clock speed to be reduced down to
0 MHz (stopped). When the oscillator is stopped, the RAM and
Special Function Registers retain their values. This mode allows
step-by-step utilization and permits reduced system power
consumption by lowering the clock frequency down to any value. For
lowest power consumption the Power Down mode is suggested.

Idle Mode

In idle mode (see Table 2), the CPU puts itself to sleep while all of
the on-chip peripherals stay active. The instruction to invoke the idle
mode is the last instruction executed in the normal operating mode
before the idle mode is activated. The CPU contents, the on-chip
RAM, and all of the special function registers remain intact during
this mode. The idle mode can be terminated either by any enabled
interrupt (at which time the process is picked up at the interrupt
service routine and continued), or by a hardware reset which starts
the processor in the same manner as a power-on reset.

Power-Down Mode

To save even more power, a Power Down mode (see Table 2) can
be invoked by software. In this mode, the oscillator is stopped and

the instruction that invoked Power Down is the last instruction
executed. The on-chip RAM and Special Function Registers retain
their values down to 2.0 V and care must be taken to return V

the minimum specified operating voltages before the Power Down
Mode is terminated.

For the P87CL5xX2, either a hardware reset or external interrupt
can be used to exit from Power Down. Reset redefines all the SFRs
but does not change the on-chip RAM. An external interrupt allows
both the SFRs and the on-chip RAM to retain their values. WUPD
(AUXR1.3Wakeup from Power Down) enables or disables the
wakeup from power down with external interrupt. Where:

WUPD = 0 Disable
WUPD = 1 Enable

To properly terminate Power Down the reset or external interrupt
should not be executed before V

is restored to its normal

operating level and must be held active long enough for the
oscillator to restart and stabilize (normally less than 10 ms).

With an external interrupt, INT0 or INT1 must be enabled and
configured as level-sensitive. Holding the pin low restarts the
oscillator but bringing the pin back high completes the exit. Once the
interrupt is serviced, the next instruction to be executed after RETI
will be the one following the instruction that put the device into
Power Down.

Design Consideration

When the idle mode is terminated by a hardware reset, the device
normally resumes program execution, from where it left off, up to
two machine cycles before the internal reset algorithm takes
control. On-chip hardware inhibits access to internal RAM in this
event, but access to the port pins is not inhibited. To eliminate the

possibility of an unexpected write when Idle is terminated by reset,

the instruction following the one that invokes Idle should not be
one that writes to a port pin or to external memory.

ONCE

Mode

The ONCE ("On-Circuit Emulation") Mode facilitates testing and
debugging of systems without the device having to be removed from
the circuit. The ONCE Mode is invoked by:

1. Pull ALE low while the device is in reset and PSEN is high;

2. Hold ALE low as RST is deactivated.

While the device is in ONCE Mode, the Port 0 pins go into a float
state, and the other port pins and ALE and PSEN are weakly pulled
high. The oscillator circuit remains active. While the P87CL5xX2 is
in this mode, an emulator or test CPU can be used to drive the
circuit. Normal operation is restored when a normal reset is applied.

Table 2. External Pin Status During Idle and Power-Down Modes

MODE

PROGRAM MEMORY

ALE

PSEN

PORT 0

PORT 1

PORT 2

PORT 3

Idle

Internal

Data

Idle

External

Float

Data

Address

Data

Power-down

Internal

Data

Power-down

External

Float

Data

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

Programmable Clock-Out

A 50% duty cycle clock can be programmed to come out on P1.0.
This pin, besides being a regular I/O pin, has two alternate
functions. It can be programmed:

1. to input the external clock for Timer/Counter 2, or

2. to output a 50% duty cycle clock ranging from 61 Hz to 4 MHz at

a 16 MHz operating frequency.

To configure the Timer/Counter 2 as a clock generator, bit C/T2 (in
T2CON) must be cleared and bit T20E in T2MOD must be set. Bit
TR2 (T2CON.2) also must be set to start the timer.

The Clock-Out frequency depends on the oscillator frequency and
the reload value of Timer 2 capture registers (RCAP2H, RCAP2L)
as shown in this equation:

Oscillator Frequency

(65536

RCAP2H, RCAP2L)

Where:

(RCAP2H,RCAP2L) = the content of RCAP2H and RCAP2L
taken as a 16-bit unsigned integer.

In the Clock-Out mode Timer 2 roll-overs will not generate an
interrupt. This is similar to when it is used as a baud-rate generator.
It is possible to use Timer 2 as a baud-rate generator and a clock
generator simultaneously. Note, however, that the baud-rate and the
Clock-Out frequency will be the same.

TIMER 0 AND TIMER 1 OPERATION

Timer 0 and Timer 1

The "Timer" or "Counter" function is selected by control bits C/T in
the Special Function Register TMOD. These two Timer/Counters
have four operating modes, which are selected by bit-pairs (M1, M0)
in TMOD. Modes 0, 1, and 2 are the same for both Timers/Counters.
Mode 3 is different. The four operating modes are described in the
following text.

Mode 0
Putting either Timer into Mode 0 makes it look like an 8048 Timer,
which is an 8-bit Counter with a divide-by-32 prescaler. Figure 2
shows the Mode 0 operation.

In this mode, the Timer register is configured as a 13-bit register. As
the count rolls over from all 1s to all 0s, it sets the Timer interrupt
flag TFn. The counted input is enabled to the Timer when TRn = 1
and either GATE = 0 or INTn = 1. (Setting GATE = 1 allows the
Timer to be controlled by external input INTn, to facilitate pulse width
measurements). TRn is a control bit in the Special Function Register
TCON (Figure 3).

The 13-bit register consists of all 8 bits of THn and the lower 5 bits
of TLn. The upper 3 bits of TLn are indeterminate and should be
ignored. Setting the run flag (TRn) does not clear the registers.

Mode 0 operation is the same for Timer 0 as for Timer 1. There are

two different GATE bits, one for Timer 1 (TMOD.7) and one for Timer

0 (TMOD.3).

Mode 1
Mode 1 is the same as Mode 0, except that the Timer register is
being run with all 16 bits.

Mode 2
Mode 2 configures the Timer register as an 8-bit Counter (TLn) with
automatic reload, as shown in Figure 4. Overflow from TLn not only
sets TFn, but also reloads TLn with the contents of THn, which is
preset by software. The reload leaves THn unchanged.

Mode 2 operation is the same for Timer 0 as for Timer 1.

Mode 3
Timer 1 in Mode 3 simply holds its count. The effect is the same as
setting TR1 = 0.

Timer 0 in Mode 3 establishes TL0 and TH0 as two separate
counters. The logic for Mode 3 on Timer 0 is shown in Figure 5. TL0
uses the Timer 0 control bits: C/T, GATE, TR0, and TF0 as well as
pin INT0. TH0 is locked into a timer function (counting machine
cycles) and takes over the use of TR1 and TF1 from Timer 1. Thus,
TH0 now controls the "Timer 1" interrupt.

Mode 3 is provided for applications requiring an extra 8-bit timer on
the counter. With Timer 0 in Mode 3, an 80C51 can look like it has
three Timer/Counters. When Timer 0 is in Mode 3, Timer 1 can be
turned on and off by switching it out of and into its own Mode 3, or
can still be used by the serial port as a baud rate generator, or in
fact, in any application not requiring an interrupt.

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

GATE

C/T

GATE

C/T

BIT

SYMBOL

FUNCTION

TMOD.3/

GATE

Gating control when set. Timer/Counter "n" is enabled only while "INTn" pin is high and

TMOD.7

"TRn" control pin is set. when cleared Timer "n" is enabled whenever "TRn" control bit is set.

TMOD.2/

C/T

Timer or Counter Selector cleared for Timer operation (input from internal system clock.)

TMOD.6

Set for Counter operation (input from "Tn" input pin).

OPERATING

8048 Timer: "TLn" serves as 5-bit prescaler.

16-bit Timer/Counter: "THn" and "TLn" are cascaded; there is no prescaler.

8-bit auto-reload Timer/Counter: "THn" holds a value which is to be reloaded
into "TLn" each time it overflows.

(Timer 0) TL0 is an 8-bit Timer/Counter controlled by the standard Timer 0 control bits.
TH0 is an 8-bit timer only controlled by Timer 1 control bits.

(Timer 1) Timer/Counter 1 stopped.

SU01580

TIMER 1

TIMER 0

Not Bit Addressable

TMOD

Address = 89H

Reset Value = 00H

Figure 1. Timer/Counter 0/1 Mode Control (TMOD) Register

INTn Pin

Timer n
Gate bit

TRn

TLn

(5 Bits)

THn

(8 Bits)

TFn

Interrupt

Control

C/T = 0

C/T = 1

SU01618

OSC

Tn Pin

*d = 6 in 6-clock mode; d = 12 in 12-clock mode.

Figure 2. Timer/Counter 0/1 Mode 0: 13-Bit Timer/Counter

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

IT0

BIT

SYMBOL

FUNCTION

TCON.7

TF1

Timer 1 overflow flag. Set by hardware on Timer/Counter overflow.
Cleared by hardware when processor vectors to interrupt routine, or clearing the bit in software.

TCON.6

TR1

Timer 1 Run control bit. Set/cleared by software to turn Timer/Counter on/off.

TCON.5

TF0

Timer 0 overflow flag. Set by hardware on Timer/Counter overflow.
Cleared by hardware when processor vectors to interrupt routine, or by clearing the bit in software.

TCON.4

TR0

Timer 0 Run control bit. Set/cleared by software to turn Timer/Counter on/off.

TCON.3

IE1

Interrupt 1 Edge flag. Set by hardware when external interrupt edge detected.
Cleared when interrupt processed.

TCON.2

IT1

Interrupt 1 type control bit. Set/cleared by software to specify falling edge/low level triggered
external interrupts.

TCON.1

IE0

Interrupt 0 Edge flag. Set by hardware when external interrupt edge detected.
Cleared when interrupt processed.

TCON.0

IT0

Interrupt 0 Type control bit. Set/cleared by software to specify falling edge/low level
triggered external interrupts.

SU01516

IE0

IT1

IE1

TR0

TF0

TR1

TF1

Bit Addressable

TCON

Address = 88H

Reset Value = 00H

Figure 3. Timer/Counter 0/1 Control (TCON) Register

TLn

(8 Bits)

TFn

Interrupt

Control

C/T = 0

C/T = 1

THn

(8 Bits)

Reload

INTn Pin

Timer n
Gate bit

TRn

SU01619

OSC

Tn Pin

*d = 6 in 6-clock mode; d = 12 in 12-clock mode.

Figure 4. Timer/Counter 0/1 Mode 2: 8-Bit Auto-Reload

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

TL0

(8 Bits)

TF0

Interrupt

Control

TH0

(8 Bits)

TF1

Interrupt

Control

TR1

INT0 Pin

Timer 0
Gate bit

TR0

SU01620

C/T = 0

C/T = 1

*d = 6 in 6-clock mode; d = 12 in 12-clock mode.

OSC

T0 Pin

Figure 5. Timer/Counter 0 Mode 3: Two 8-Bit Counters

TIMER 2 OPERATION

Timer 2

Timer 2 is a 16-bit Timer/Counter which can operate as either an
event timer or an event counter, as selected by C/T2* in the special
function register T2CON (see Figure 1). Timer 2 has three operating
modes:Capture, Auto-reload (up or down counting) ,and Baud Rate
Generator, which are selected by bits in the T2CON as shown in
Table 3.

Capture Mode

In the capture mode there are two options which are selected by bit
EXEN2 in T2CON. If EXEN2 = 0, then timer 2 is a 16-bit timer or
counter (as selected by C/T2* in T2CON) which, upon overflowing
sets bit TF2, the timer 2 overflow bit. This bit can be used to
generate an interrupt (by enabling the Timer 2 interrupt bit in the
IE register). If EXEN2 = 1, Timer 2 operates as described above, but
with the added feature that a 1- to -0 transition at external input
T2EX causes the current value in the Timer 2 registers, TL2 and
TH2, to be captured into registers RCAP2L and RCAP2H,
respectively. In addition, the transition at T2EX causes bit EXF2 in
T2CON to be set, and EXF2 like TF2 can generate an interrupt
(which vectors to the same location as Timer 2 overflow interrupt.
The Timer 2 interrupt service routine can interrogate TF2 and EXF2
to determine which event caused the interrupt). The capture mode is
illustrated in Figure 2 (There is no reload value for TL2 and TH2 in
this mode. Even when a capture event occurs from T2EX, the
counter keeps on counting T2EX pin transitions or osc/12 pulses.).

Auto-Reload Mode (Up or Down Counter)

In the 16-bit auto-reload mode, Timer 2 can be configured (as either
a timer or counter (C/T2* in T2CON)) then programmed to count up
or down. The counting direction is determined by bit DCEN (Down
Counter Enable) which is located in the T2MOD register (see

Figure 3). When reset is applied the DCEN = 0 which means Timer
2 will default to counting up. If DCEN bit is set, Timer 2 can count up
or down depending on the value of the T2EX pin.

Figure 4 shows Timer 2 which will count up automatically since
DCEN = 0. In this mode there are two options selected by bit
EXEN2 in T2CON register. If EXEN2 = 0, then Timer 2 counts up to
0FFFFH and sets the TF2 (Overflow Flag) bit upon overflow. This
causes the Timer 2 registers to be reloaded with the 16-bit value in
RCAP2L and RCAP2H. The values in RCAP2L and RCAP2H are
preset by software means.

If EXEN2 = 1, then a 16-bit reload can be triggered either by an
overflow or by a 1-to-0 transition at input T2EX. This transition also
sets the EXF2 bit. The Timer 2 interrupt, if enabled, can be
generated when either TF2 or EXF2 are 1.

In Figure 5 DCEN = 1 which enables Timer 2 to count up or down.
This mode allows pin T2EX to control the direction of count. When a
logic 1 is applied at pin T2EX Timer 2 will count up. Timer 2 will
overflow at 0FFFFH and set the TF2 flag, which can then generate
an interrupt, if the interrupt is enabled. This timer overflow also
causes the 16bit value in RCAP2L and RCAP2H to be reloaded
into the timer registers TL2 and TH2.

When a logic 0 is applied at pin T2EX this causes Timer 2 to count
down. The timer will underflow when TL2 and TH2 become equal to
the value stored in RCAP2L and RCAP2H. Timer 2 underflow sets
the TF2 flag and causes 0FFFFH to be reloaded into the timer
registers TL2 and TH2.

The external flag EXF2 toggles when Timer 2 underflows or
overflows. This EXF2 bit can be used as a 17th bit of resolution if
needed. The EXF2 flag does not generate an interrupt in this mode
of operation.

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Product data

P87CL52X2/54X2

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2003 May 14

Table 3. Timer 2 Operating Modes

RCLK + TCLK

CP/RL2

TR2

MODE

16-bit Auto-reload

16-bit Capture

Baud rate generator

(off)

(MSB)

(LSB)

Symbol

Position

Name and Significance

TF2

T2CON.7

Timer 2 overflow flag set by a Timer 2 overflow and must be cleared by software. TF2 will not be set
when either RCLK or TCLK = 1.

EXF2

T2CON.6

Timer 2 external flag set when either a capture or reload is caused by a negative transition on T2EX and
EXEN2 = 1. When Timer 2 interrupt is enabled, EXF2 = 1 will cause the CPU to vector to the Timer 2
interrupt routine. EXF2 must be cleared by software. EXF2 does not cause an interrupt in up/down
counter mode (DCEN = 1).

RCLK

T2CON.5

Receive clock flag. When set, causes the serial port to use Timer 2 overflow pulses for its receive clock
in modes 1 and 3. RCLK = 0 causes Timer 1 overflow to be used for the receive clock.

TCLK

T2CON.4

Transmit clock flag. When set, causes the serial port to use Timer 2 overflow pulses for its transmit clock
in modes 1 and 3. TCLK = 0 causes Timer 1 overflows to be used for the transmit clock.

EXEN2

T2CON.3

Timer 2 external enable flag. When set, allows a capture or reload to occur as a result of a negative
transition on T2EX if Timer 2 is not being used to clock the serial port. EXEN2 = 0 causes Timer 2 to
ignore events at T2EX.

TR2

T2CON.2

Start/stop control for Timer 2. A logic 1 starts the timer.

C/T2

T2CON.1

Timer or counter select. (Timer 2)

0 = Internal timer (OSC/12)
1 = External event counter (falling edge triggered).

CP/RL2

T2CON.0

Capture/Reload flag. When set, captures will occur on negative transitions at T2EX if EXEN2 = 1. When
cleared, auto-reloads will occur either with Timer 2 overflows or negative transitions at T2EX when
EXEN2 = 1. When either RCLK = 1 or TCLK = 1, this bit is ignored and the timer is forced to auto-reload
on Timer 2 overflow.

TF2

EXF2

RCLK

TCLK

EXEN2

TR2

C/T2

CP/RL2

SU00728

Figure 1. Timer/Counter 2 (T2CON) Control Register

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2003 May 14

Baud Rate Generator Mode

Bits TCLK and/or RCLK in T2CON (Table 3) allow the serial port
transmit and receive baud rates to be derived from either Timer 1 or
Timer 2. When TCLK = 0, Timer 1 is used as the serial port transmit
baud rate generator. When TCLK= 1, Timer 2 is used as the serial
port transmit baud rate generator. RCLK has the same effect for the
serial port receive baud rate. With these two bits, the serial port can
have different receive and transmit baud rates one generated by
Timer 1, the other by Timer 2.

Figure 6 shows the Timer 2 in baud rate generation mode. The baud
rate generation mode is like the auto-reload mode, in that a rollover
in TH2 causes the Timer 2 registers to be reloaded with the 16-bit
value in registers RCAP2H and RCAP2L, which are preset by
software.

The baud rates in modes 1 and 3 are determined by Timer 2's
overflow rate given below:

Modes 1 and 3 Baud Rates

Timer 2 Overflow Rate

The timer can be configured for either "timer" or "counter" operation.
In many applications, it is configured for "timer" operation
(C/T2* = 0). Timer operation is different for Timer 2 when it is being
used as a baud rate generator.

Usually, as a timer it would increment every machine cycle (i.e., 1/12
the oscillator frequency). As a baud rate generator, it increments
every state time (i.e., 1/2 the oscillator frequency). Thus the baud
rate formula is as follows:

Oscillator Frequency

[32

[65536

(RCAP2H, RCAP2L)]]

Modes 1 and 3 Baud Rates =

Where:

(RCAP2H, RCAP2L) = The content of RCAP2H and

RCAP2L taken as a 16-bit unsigned integer.

The Timer 2 as a baud rate generator mode shown in Figure 6, is
valid only if RCLK and/or TCLK = 1 in T2CON register. Note that a
rollover in TH2 does not set TF2, and will not generate an interrupt.
Thus, the Timer 2 interrupt does not have to be disabled when
Timer 2 is in the baud rate generator mode. Also if the EXEN2
(T2 external enable flag) is set, a 1-to-0 transition in T2EX
(Timer/counter 2 trigger input) will set EXF2 (T2 external flag) but
will not cause a reload from (RCAP2H, RCAP2L) to (TH2,TL2).
Therefore when Timer 2 is in use as a baud rate generator, T2EX
can be used as an additional external interrupt, if needed.

When Timer 2 is in the baud rate generator mode, one should not try
to read or write TH2 and TL2. As a baud rate generator, Timer 2 is
incremented every state time (osc/2) or asynchronously from pin T2;

under these conditions, a read or write of TH2 or TL2 may not be
accurate. The RCAP2 registers may be read, but should not be
written to, because a write might overlap a reload and cause write
and/or reload errors. The timer should be turned off (clear TR2)
before accessing the Timer 2 or RCAP2 registers.

Table 4 shows commonly used baud rates and how they can be
obtained from Timer 2.

Table 4. Timer 2 Generated Commonly Used

Baud Rates

Ba d Rate

Osc Freq

Timer 2

Baud Rate

Osc Freq

RCAP2H

RCAP2L

375 K

12 MHz

9.6 K

12 MHz

2.8 K

12 MHz

2.4 K

12 MHz

1.2 K

12 MHz

300

12 MHz

110

12 MHz

300

6 MHz

110

6 MHz

Summary Of Baud Rate Equations

Timer 2 is in baud rate generating mode. If Timer 2 is being clocked
through pin T2(P1.0) the baud rate is:

Baud Rate

Timer 2 Overflow Rate

If Timer 2 is being clocked internally, the baud rate is:

Baud Rate

OSC

[32

[65536

(RCAP2H, RCAP2L)]]

Where f

OSC

= Oscillator Frequency

To obtain the reload value for RCAP2H and RCAP2L, the above
equation can be rewritten as:

RCAP2H, RCAP2L

65536

OSC

Baud Rate

Timer/Counter 2 Set-up

Except for the baud rate generator mode, the values given for
T2CON do not include the setting of the TR2 bit. Therefore, bit TR2
must be set, separately, to turn the timer on. See Table 5 for set-up
of Timer 2 as a timer. Also see Table 6 for set-up of Timer 2 as a
counter.

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Product data

P87CL52X2/54X2

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(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

FULL-DUPLEX ENHANCED UART

Standard UART operation

The serial port is full duplex, meaning it can transmit and receive
simultaneously. It is also receive-buffered, meaning it can
commence reception of a second byte before a previously received
byte has been read from the register. (However, if the first byte still
hasn't been read by the time reception of the second byte is
complete, one of the bytes will be lost.) The serial port receive and
transmit registers are both accessed at Special Function Register
SBUF. Writing to SBUF loads the transmit register, and reading
SBUF accesses a physically separate receive register.

The serial port can operate in 4 modes:

Mode 0:

Serial data enters and exits through RxD. TxD outputs
the shift clock. 8 bits are transmitted/received (LSB first).
The baud rate is fixed at 1/12 the oscillator frequency in
12-clock mode or 1/6 the oscillator frequency in 6-clock
mode.

Mode 1:

10 bits are transmitted (through TxD) or received
(through RxD): a start bit (0), 8 data bits (LSB first), and
a stop bit (1). On receive, the stop bit goes into RB8 in
Special Function Register SCON. The baud rate is
variable.

Mode 2:

11 bits are transmitted (through TxD) or received
(through RxD): start bit (0), 8 data bits (LSB first), a
programmable 9th data bit, and a stop bit (1). On
Transmit, the 9th data bit (TB8 in SCON) can be
assigned the value of 0 or 1. Or, for example, the parity
bit (P, in the PSW) could be moved into TB8. On receive,
the 9th data bit goes into RB8 in Special Function
Register SCON, while the stop bit is ignored. The baud
rate is programmable to either 1/32 or 1/64 the oscillator
frequency in 12-clock mode or 1/16 or 1/32 the oscillator
frequency in 6-clock mode.

Mode 3:

11 bits are transmitted (through TxD) or received
(through RxD): a start bit (0), 8 data bits (LSB first), a
programmable 9th data bit, and a stop bit (1). In fact,
Mode 3 is the same as Mode 2 in all respects except
baud rate. The baud rate in Mode 3 is variable.

In all four modes, transmission is initiated by any instruction that

uses SBUF as a destination register. Reception is initiated in Mode 0

by the condition RI = 0 and REN = 1. Reception is initiated in the
other modes by the incoming start bit if REN = 1.

Multiprocessor Communications
Modes 2 and 3 have a special provision for multiprocessor
communications. In these modes, 9 data bits are received. The 9th
one goes into RB8. Then comes a stop bit. The port can be
programmed such that when the stop bit is received, the serial port
interrupt will be activated only if RB8 = 1. This feature is enabled by
setting bit SM2 in SCON. A way to use this feature in multiprocessor
systems is as follows:

When the master processor wants to transmit a block of data to one
of several slaves, it first sends out an address byte which identifies
the target slave. An address byte differs from a data byte in that the
9th bit is 1 in an address byte and 0 in a data byte. With SM2 = 1, no
slave will be interrupted by a data byte. An address byte, however,
will interrupt all slaves, so that each slave can examine the received
byte and see if it is being addressed. The addressed slave will clear
its SM2 bit and prepare to receive the data bytes that will be coming.

The slaves that weren't being addressed leave their SM2s set and
go on about their business, ignoring the coming data bytes.

SM2 has no effect in Mode 0, and in Mode 1 can be used to check
the validity of the stop bit. In a Mode 1 reception, if SM2 = 1, the
receive interrupt will not be activated unless a valid stop bit is
received.

Serial Port Control Register
The serial port control and status register is the Special Function
Register SCON, shown in Figure 7. This register contains not only
the mode selection bits, but also the 9th data bit for transmit and
receive (TB8 and RB8), and the serial port interrupt bits (TI and RI).

Baud Rates
The baud rate in Mode 0 is fixed: Mode 0 Baud Rate = Oscillator
Frequency / 12 (12-clock mode) or / 6 (6-clock mode). The baud
rate in Mode 2 depends on the value of bit SMOD in Special
Function Register PCON. If SMOD = 0 (which is the value on reset),
and the port pins in 12-clock mode, the baud rate is 1/64 the
oscillator frequency. If SMOD = 1, the baud rate is 1/32 the oscillator
frequency. In 6-clock mode, the baud rate is 1/32 or 1/16 the
oscillator frequency, respectively.

Mode 2 Baud Rate =

SMOD

(Oscillator Frequency)

Where:

n = 64 in 12-clock mode, 32 in 6-clock mode

The baud rates in Modes 1 and 3 are determined by the Timer 1 or
Timer 2 overflow rate.

Using Timer 1 to Generate Baud Rates
When Timer 1 is used as the baud rate generator
(T2CON.RCLK = 0, T2CON.TCLK = 0), the baud rates in Modes 1
and 3 are determined by the Timer 1 overflow rate and the value of
SMOD as follows:

Mode 1, 3 Baud Rate =

SMOD

(Timer 1 Overflow Rate)

Where:

n = 32 in 12-clock mode, 16 in 6-clock mode

The Timer 1 interrupt should be disabled in this application. The
Timer itself can be configured for either "timer" or "counter"
operation, and in any of its 3 running modes. In the most typical
applications, it is configured for "timer" operation, in the auto-reload
mode (high nibble of TMOD = 0010B). In that case the baud rate is
given by the formula:

Mode 1, 3 Baud Rate =

SMOD

Oscillator Frequency

[256(TH1)]

Where:

n = 32 in 12-clock mode, 16 in 6-clock mode

One can achieve very low baud rates with Timer 1 by leaving the
Timer 1 interrupt enabled, and configuring the Timer to run as a
16-bit timer (high nibble of TMOD = 0001B), and using the Timer 1
interrupt to do a 16-bit software reload. Figure 8 lists various
commonly used baud rates and how they can be obtained from
Timer 1.

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P87CL52X2/54X2

80C51 8-bit microcontroller family

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2003 May 14

SM2

Enables the multiprocessor communication feature in Modes 2 and 3. In Mode 2 or 3, if SM2 is set to 1, then Rl will not be
activated if the received 9th data bit (RB8) is 0. In Mode 1, if SM2=1 then RI will not be activated if a valid stop bit was not
received. In Mode 0, SM2 should be 0.

REN

Enables serial reception. Set by software to enable reception. Clear by software to disable reception.

TB8

The 9th data bit that will be transmitted in Modes 2 and 3. Set or clear by software as desired.

RB8

In Modes 2 and 3, is the 9th data bit that was received. In Mode 1, it SM2=0, RB8 is the stop bit that was received. In Mode 0,
RB8 is not used.

Transmit interrupt flag. Set by hardware at the end of the 8th bit time in Mode 0, or at the beginning of the stop bit in the other
modes, in any serial transmission. Must be cleared by software.

Receive interrupt flag. Set by hardware at the end of the 8th bit time in Mode 0, or halfway through the stop bit time in the other
modes, in any serial reception (except see SM2). Must be cleared by software.

SM0

SM1

SM2

REN

TB8

RB8

Where SM0, SM1 specify the serial port mode, as follows:

SM0

SM1

Mode

Description

Baud Rate

shift register

OSC

/12 (12-clock mode) or f

OSC

/6 (6-clock mode)

8-bit UART

variable

9-bit UART

OSC

/64 or f

OSC

/32 (12-clock mode) or f

OSC

/32 or f

OSC

/16 (6-clock mode)

3 9-bit

UART

variable

SU01626

Bit Addressable

SCON

Address = 98H

Reset Value = 00H

Figure 7. Serial Port Control (SCON) Register

Baud Rate

SMOD

Timer 1

Mode

12-clock mode

6-clock mode

OSC

SMOD

C/T

Mode

Reload Value

Mode 0 Max

1.67 MHz

3.34 MHz

20 MHz

Mode 2 Max

625 k

1250 k

20 MHz

Mode 1, 3 Max

104.2 k

208.4 k

20 MHz

FFH

Mode 1, 3

19.2 k

38.4 k

11.059 MHz

FDH

9.6 k

19.2 k

11.059 MHz

FDH

4.8 k

9.6 k

11.059 MHz

FAH

2.4 k

4.8 k

11.059 MHz

F4H

1.2 k

2.4 k

11.059 MHz

E8H

137.5

275

11.986 MHz

1DH

110

220

6 MHz

72H

110

220

12 MHz

FEEBH

Figure 8. Timer 1 Generated Commonly Used Baud Rates

More About Mode 0
Serial data enters and exits through RxD. TxD outputs the shift
clock. 8 bits are transmitted/received: 8 data bits (LSB first). The
baud rate is fixed a 1/12 the oscillator frequency (12-clock mode) or
1/6 the oscillator frequency (6-clock mode).

Figure 9 shows a simplified functional diagram of the serial port in
Mode 0, and associated timing.

Transmission is initiated by any instruction that uses SBUF as a
destination register. The "write to SBUF" signal at S6P2 also loads a
1 into the 9th position of the transmit shift register and tells the TX
Control block to commence a transmission. The internal timing is
such that one full machine cycle will elapse between "write to SBUF"
and activation of SEND.

SEND enables the output of the shift register to the alternate output
function line of P3.0 and also enable SHIFT CLOCK to the alternate

output function line of P3.1. SHIFT CLOCK is low during S3, S4, and

S5 of every machine cycle, and high during S6, S1, and S2. At

S6P2 of every machine cycle in which SEND is active, the contents
of the transmit shift are shifted to the right one position.

As data bits shift out to the right, zeros come in from the left. When
the MSB of the data byte is at the output position of the shift register,
then the 1 that was initially loaded into the 9th position, is just to the
left of the MSB, and all positions to the left of that contain zeros.
This condition flags the TX Control block to do one last shift and
then deactivate SEND and set T1. Both of these actions occur at
S1P1 of the 10th machine cycle after "write to SBUF."

Reception is initiated by the condition REN = 1 and R1 = 0. At
S6P2 of the next machine cycle, the RX Control unit writes the bits
11111110 to the receive shift register, and in the next clock phase
activates RECEIVE.

RECEIVE enable SHIFT CLOCK to the alternate output function line
of P3.1. SHIFT CLOCK makes transitions at S3P1 and S6P1 of
every machine cycle. At S6P2 of every machine cycle in which
RECEIVE is active, the contents of the receive shift register are

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2003 May 14

shifted to the left one position. The value that comes in from the right

is the value that was sampled at the P3.0 pin at S5P2 of the same
machine cycle.

As data bits come in from the right, 1s shift out to the left. When the
0 that was initially loaded into the rightmost position arrives at the
leftmost position in the shift register, it flags the RX Control block to
do one last shift and load SBUF. At S1P1 of the 10th machine cycle
after the write to SCON that cleared RI, RECEIVE is cleared as RI is
set.

More About Mode 1
Ten bits are transmitted (through TxD), or received (through RxD): a
start bit (0), 8 data bits (LSB first), and a stop bit (1). On receive, the
stop bit goes into RB8 in SCON. In the 80C51 the baud rate is
determined by the Timer 1 or Timer 2 overflow rate.

Figure 10 shows a simplified functional diagram of the serial port in
Mode 1, and associated timings for transmit receive.

Transmission is initiated by any instruction that uses SBUF as a
destination register. The "write to SBUF" signal also loads a 1 into
the 9th bit position of the transmit shift register and flags the TX
Control unit that a transmission is requested. Transmission actually
commences at S1P1 of the machine cycle following the next rollover
in the divide-by-16 counter. (Thus, the bit times are synchronized to
the divide-by-16 counter, not to the "write to SBUF" signal.)

The transmission begins with activation of SEND which puts the
start bit at TxD. One bit time later, DATA is activated, which enables
the output bit of the transmit shift register to TxD. The first shift pulse
occurs one bit time after that.

As data bits shift out to the right, zeros are clocked in from the left.
When the MSB of the data byte is at the output position of the shift
register, then the 1 that was initially loaded into the 9th position is
just to the left of the MSB, and all positions to the left of that contain
zeros. This condition flags the TX Control unit to do one last shift
and then deactivate SEND and set TI. This occurs at the 10th
divide-by-16 rollover after "write to SBUF."

Reception is initiated by a detected 1-to-0 transition at RxD. For this
purpose RxD is sampled at a rate of 16 times whatever baud rate
has been established. When a transition is detected, the
divide-by-16 counter is immediately reset, and 1FFH is written into
the input shift register. Resetting the divide-by-16 counter aligns its
rollovers with the boundaries of the incoming bit times.

The 16 states of the counter divide each bit time into 16ths. At the
7th, 8th, and 9th counter states of each bit time, the bit detector
samples the value of RxD. The value accepted is the value that was
seen in at least 2 of the 3 samples. This is done for noise rejection.
If the value accepted during the first bit time is not 0, the receive
circuits are reset and the unit goes back to looking for another 1-to-0
transition. This is to provide rejection of false start bits. If the start bit
proves valid, it is shifted into the input shift register, and reception of
the rest of the frame will proceed.

As data bits come in from the right, 1s shift out to the left. When the
start bit arrives at the leftmost position in the shift register (which in
mode 1 is a 9-bit register), it flags the RX Control block to do one
last shift, load SBUF and RB8, and set RI. The signal to load SBUF
and RB8, and to set RI, will be generated if, and only if, the following
conditions are met at the time the final shift pulse is generated.:
1. R1 = 0, and
2. Either SM2 = 0, or the received stop bit = 1.

If either of these two conditions is not met, the received frame is
irretrievably lost. If both conditions are met, the stop bit goes into
RB8, the 8 data bits go into SBUF, and RI is activated. At this time,

whether the above conditions are met or not, the unit goes back to
looking for a 1-to-0 transition in RxD.

More About Modes 2 and 3
Eleven bits are transmitted (through TxD), or received (through
RxD): a start bit (0), 8 data bits (LSB first), a programmable 9th data
bit, and a stop bit (1). On transmit, the 9th data bit (TB8) can be
assigned the value of 0 or 1. On receive, the 9the data bit goes into
RB8 in SCON. The baud rate is programmable to either 1/32 or 1/64
(12-clock mode) or 1/16 or 1/32 the oscillator frequency (6-clock
mode) the oscillator frequency in Mode 2. Mode 3 may have a
variable baud rate generated from Timer 1 or Timer 2.

Figures 11 and 12 show a functional diagram of the serial port in
Modes 2 and 3. The receive portion is exactly the same as in Mode
1. The transmit portion differs from Mode 1 only in the 9th bit of the
transmit shift register.

Transmission is initiated by any instruction that uses SBUF as a
destination register. The "write to SBUF" signal also loads TB8 into
the 9th bit position of the transmit shift register and flags the TX
Control unit that a transmission is requested. Transmission
commences at S1P1 of the machine cycle following the next rollover
in the divide-by-16 counter. (Thus, the bit times are synchronized to
the divide-by-16 counter, not to the "write to SBUF" signal.)

The transmission begins with activation of SEND, which puts the
start bit at TxD. One bit time later, DATA is activated, which enables
the output bit of the transmit shift register to TxD. The first shift pulse
occurs one bit time after that. The first shift clocks a 1 (the stop bit)
into the 9th bit position of the shift register. Thereafter, only zeros
are clocked in. Thus, as data bits shift out to the right, zeros are
clocked in from the left. When TB8 is at the output position of the
shift register, then the stop bit is just to the left of TB8, and all
positions to the left of that contain zeros. This condition flags the TX
Control unit to do one last shift and then deactivate SEND and set

TI. This occurs at the 11th divide-by-16 rollover after "write to SUBF."

At the 7th, 8th, and 9th counter states of each bit time, the bit
detector samples the value of R-D. The value accepted is the value
that was seen in at least 2 of the 3 samples. If the value accepted
during the first bit time is not 0, the receive circuits are reset and the
unit goes back to looking for another 1-to-0 transition. If the start bit
proves valid, it is shifted into the input shift register, and reception of
the rest of the frame will proceed.

As data bits come in from the right, 1s shift out to the left. When the
start bit arrives at the leftmost position in the shift register (which in
Modes 2 and 3 is a 9-bit register), it flags the RX Control block to do
one last shift, load SBUF and RB8, and set RI.

The signal to load SBUF and RB8, and to set RI, will be generated
if, and only if, the following conditions are met at the time the final
shift pulse is generated.
1. RI = 0, and
2. Either SM2 = 0, or the received 9th data bit = 1.

If either of these conditions is not met, the received frame is
irretrievably lost, and RI is not set. If both conditions are met, the
received 9th data bit goes into RB8, and the first 8 data bits go into
SBUF. One bit time later, whether the above conditions were met or
not, the unit goes back to looking for a 1-to-0 transition at the RxD
input.

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

Enhanced UART

The UART operates in all of the usual modes that are described in
the first section of

Data Handbook IC20, 80C51-Based 8-Bit

Microcontrollers. In addition the UART can perform framing error
detect by looking for missing stop bits, and automatic address
recognition. The P87CL5xX2 UART also fully supports
multiprocessor communication.

When used for framing error detect the UART looks for missing stop
bits in the communication. A missing bit will set the FE bit in the
SCON register. The FE bit shares the SCON.7 bit with SM0 and the
function of SCON.7 is determined by PCON.6 (SMOD0) (see
Figure 13). If SMOD0 is set then SCON.7 functions as FE. SCON.7
functions as SM0 when SMOD0 is cleared. When used as FE
SCON.7 can only be cleared by software. Refer to Figure 14.

Automatic Address Recognition
Automatic Address Recognition is a feature which allows the UART
to recognize certain addresses in the serial bit stream by using
hardware to make the comparisons. This feature saves a great deal
of software overhead by eliminating the need for the software to
examine every serial address which passes by the serial port. This
feature is enabled by setting the SM2 bit in SCON. In the 9 bit UART
modes, mode 2 and mode 3, the Receive Interrupt flag (RI) will be
automatically set when the received byte contains either the "Given"
address or the "Broadcast" address. The 9 bit mode requires that
the 9th information bit is a 1 to indicate that the received information
is an address and not data. Automatic address recognition is shown
in Figure 15.

The 8 bit mode is called Mode 1. In this mode the RI flag will be set
if SM2 is enabled and the information received has a valid stop bit
following the 8 address bits and the information is either a Given or
Broadcast address.

Mode 0 is the Shift Register mode and SM2 is ignored.

Using the Automatic Address Recognition feature allows a master to
selectively communicate with one or more slaves by invoking the
Given slave address or addresses. All of the slaves may be
contacted by using the Broadcast address. Two special Function
Registers are used to define the slave's address, SADDR, and the
address mask, SADEN. SADEN is used to define which bits in the
SADDR are to b used and which bits are "don't care". The SADEN
mask can be logically ANDed with the SADDR to create the "Given"
address which the master will use for addressing each of the slaves.
Use of the Given address allows multiple slaves to be recognized
while excluding others. The following examples will help to show the
versatility of this scheme:

Slave 0

SADDR

1100 0000

SADEN

1111 1101

Given

1100 00X0

Slave 1

SADDR

1100 0000

SADEN

1111 1110

Given

1100 000X

In the above example SADDR is the same and the SADEN data is
used to differentiate between the two slaves. Slave 0 requires a 0 in
bit 0 and it ignores bit 1. Slave 1 requires a 0 in bit 1 and bit 0 is
ignored. A unique address for Slave 0 would be 1100 0010 since
slave 1 requires a 0 in bit 1. A unique address for slave 1 would be
1100 0001 since a 1 in bit 0 will exclude slave 0. Both slaves can be
selected at the same time by an address which has bit 0 = 0 (for
slave 0) and bit 1 = 0 (for slave 1). Thus, both could be addressed
with 1100 0000.

In a more complex system the following could be used to select
slaves 1 and 2 while excluding slave 0:

Slave 0

SADDR

1100 0000

SADEN

1111 1001

Given

1100 0XX0

Slave 1

SADDR

1110 0000

SADEN

1111 1010

Given

1110 0X0X

Slave 2

SADDR

1110 0000

SADEN

1111 1100

Given

1110 00XX

In the above example the differentiation among the 3 slaves is in the
lower 3 address bits. Slave 0 requires that bit 0 = 0 and it can be

uniquely addressed by 1110 0110. Slave 1 requires that bit 1 = 0 and

it can be uniquely addressed by 1110 and 0101. Slave 2 requires
that bit 2 = 0 and its unique address is 1110 0011. To select Slaves 0
and 1 and exclude Slave 2 use address 1110 0100, since it is
necessary to make bit 2 = 1 to exclude slave 2.

The Broadcast Address for each slave is created by taking the
logical OR of SADDR and SADEN. Zeros in this result are trended
as don't-cares. In most cases, interpreting the don't-cares as ones,
the broadcast address will be FF hexadecimal.

Upon reset SADDR (SFR address 0A9H) and SADEN (SFR
address 0B9H) are leaded with 0s. This produces a given address
of all "don't cares" as well as a Broadcast address of all "don't
cares". This effectively disables the Automatic Addressing mode and
allows the microcontroller to use standard 80C51 type UART drivers
which do not make use of this feature.

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

SCON Address = 98H

Reset Value = 0000 0000B

SM0/FE

SM1

SM2

REN

TB8

RB8

Bit Addressable

(SMOD0 = 0/1)*

Symbol

Function

Framing Error bit. This bit is set by the receiver when an invalid stop bit is detected. The FE bit is not cleared by valid
frames but should be cleared by software. The SMOD0 bit must be set to enable access to the FE bit.

SM0

Serial Port Mode Bit 0, (SMOD0 must = 0 to access bit SM0)

SM1

Serial Port Mode Bit 1
SM0

SM1

Mode

Description

Baud Rate**

shift register

OSC

/12

8-bit UART

variable

9-bit UART

OSC

/64 or f

OSC

/32

9-bit UART

variable

SM2

Enables the Automatic Address Recognition feature in Modes 2 or 3. If SM2 = 1 then Rl will not be set unless the
received 9th data bit (RB8) is 1, indicating an address, and the received byte is a Given or Broadcast Address.
In Mode 1, if SM2 = 1 then Rl will not be activated unless a valid stop bit was received, and the received byte is a
Given or Broadcast Address. In Mode 0, SM2 should be 0.

REN

Enables serial reception. Set by software to enable reception. Clear by software to disable reception.

TB8

The 9th data bit that will be transmitted in Modes 2 and 3. Set or clear by software as desired.

RB8

In modes 2 and 3, the 9th data bit that was received. In Mode 1, if SM2 = 0, RB8 is the stop bit that was received.
In Mode 0, RB8 is not used.

Transmit interrupt flag. Set by hardware at the end of the 8th bit time in Mode 0, or at the beginning of the stop bit in the
other modes, in any serial transmission. Must be cleared by software.

Receive interrupt flag. Set by hardware at the end of the 8th bit time in Mode 0, or halfway through the stop bit time in
the other modes, in any serial reception (except see SM2). Must be cleared by software.

NOTE:
*SMOD0 is located at PCON6.
**f

OSC

= oscillator frequency

SU00043

Bit:

Figure 13. SCON: Serial Port Control Register

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

Interrupt Priority Structure

The P87CL5xX2 has a 6-source four-level interrupt structure. They
are the IE, IP and IPH. (See Figures 16, 17, and 18.) The IPH
(Interrupt Priority High) register that makes the four-level interrupt
structure possible. The IPH is located at SFR address B7H. The
structure of the IPH register and a description of its bits is shown in
Figure 18.

The function of the IPH SFR is simple and when combined with the
IP SFR determines the priority of each interrupt. The priority of each
interrupt is determined as shown in the following table:

PRIORITY BITS

INTERRUPT PRIORITY LEVEL

IPH.x

IP.x

INTERRUPT PRIORITY LEVEL

Level 0 (lowest priority)

Level 1

Level 2

Level 3 (highest priority)

An interrupt will be serviced as long as an interrupt of equal or
higher priority is not already being serviced. If an interrupt of equal
or higher level priority is being serviced, the new interrupt will wait
until it is finished before being serviced. If a lower priority level
interrupt is being serviced, it will be stopped and the new interrupt
serviced. When the new interrupt is finished, the lower priority level
interrupt that was stopped will be completed.

Table 7.

Interrupt Table

SOURCE

POLLING PRIORITY

REQUEST BITS

HARDWARE CLEAR?

VECTOR ADDRESS

IE0

N (L)

Y (T)

03H

TP0

0BH

IE1

N (L)

Y (T)

13H

TF1

1BH

RI, TI

23H

TF2, EXF2

2BH

NOTES:
1. L = Level activated
2. T = Transition activated

EX0

IE (0A8H)

Enable Bit = 1 enables the interrupt.
Enable Bit = 0 disables it.

BIT

SYMBOL

FUNCTION

IE.7

Global disable bit. If EA = 0, all interrupts are disabled. If EA = 1, each interrupt can be individually
enabled or disabled by setting or clearing its enable bit.

IE.6

Not implemented. Reserved for future use.

IE.5

ET2

Timer 2 interrupt enable bit.

IE.4

Serial Port interrupt enable bit.

IE.3

ET1

Timer 1 interrupt enable bit.

IE.2

EX1

External interrupt 1 enable bit.

IE.1

ET0

Timer 0 interrupt enable bit.

IE.0

EX0

External interrupt 0 enable bit.

SU00571

ET0

EX1

ET1

ET2

Figure 16. IE Registers

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

Reduced EMI Mode

The AO bit (AUXR.0) in the AUXR register when set disables the
ALE output.

Reduced EMI Mode

AUXR (8EH)

AUXR.0

Turns off ALE output.

Dual DPTR

The dual DPTR structure (see Figure 19) enables a way to specify
the address of an external data memory location. There are two
16-bit DPTR registers that address the external memory, and a
single bit called DPS = AUXR1/bit0 that allows the program code to
switch between them.

New Register Name: AUXR1#

SFR Address: A2H

Reset Value: xxx000x0B

AUXR1 (A2H)

WUPD

DPS

Where:

DPS = AUXR1/bit0 = Switches between DPTR0 and DPTR1.

Select Reg

DPS

DPTR0

DPTR1

The DPS bit status should be saved by software when switching
between DPTR0 and DPTR1.

Note that bit 2 is not writable and is always read as a zero. This
allows the DPS bit to be quickly toggled simply by executing an INC
DPTR instruction without affecting the WOPD or LPEP bits.

DPS

DPTR1

DPTR0

DPH

(83H)

DPL

(82H)

EXTERNAL

DATA

MEMORY

SU00745A

BIT0

AUXR1

Figure 19.

DPTR Instructions
The instructions that refer to DPTR refer to the data pointer that is
currently selected using the AUXR1/bit 0 register. The six
instructions that use the DPTR are as follows:

INC DPTR

Increments the data pointer by 1

MOV DPTR, #data16

Loads the DPTR with a 16-bit constant

MOV A, @ A+DPTR

Move code byte relative to DPTR to ACC

MOVX A, @ DPTR

Move external RAM (16-bit address) to
ACC

MOVX @ DPTR , A

Move ACC to external RAM (16-bit
address)

JMP @ A + DPTR

Jump indirect relative to DPTR

The data pointer can be accessed on a byte-by-byte basis by
specifying the low or high byte in an instruction which accesses the
SFRs. See application note AN458 for more details.

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

ABSOLUTE MAXIMUM RATINGS

1, 2, 3

PARAMETER

RATING

UNIT

Operating temperature under bias

0 to +70

Storage temperature range

65 to +150

Voltage on EA pin to V

0 to +13.0

Voltage on any other pin to V

0.5 to +6.5

Maximum I

per I/O pin

Power dissipation (based on package heat transfer limitations, not device power consumption)

1.5

NOTES:
1. Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and

functional operation of the device at these or any conditions other than those described in the AC and DC Electrical Characteristics section
of this specification is not implied.

2. This product includes circuitry specifically designed for the protection of its internal devices from the damaging effects of excessive static

charge. Nonetheless, it is suggested that conventional precautions be taken to avoid applying greater than the rated maximum.

3. Parameters are valid over operating temperature range unless otherwise specified. All voltages are with respect to V

unless otherwise

noted.

AC ELECTRICAL CHARACTERISTICS

amb

= 0

C to +70

C or 40

C to +85

CLOCK FREQUENCY

RANGE f

SYMBOL

FIGURE

PARAMETER

MIN

MAX

UNIT

1/t

CLCL

Oscillator frequency

Operating mode: 6-clock

12-clock

0
0

16
33

MHz
MHz

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

DC ELECTRICAL CHARACTERISTICS

amb

= 0

C to +70

C, V

= 1.8 V to 3.3 V, V

= 0 V (12 MHz devices)

SYMBOL

PARAMETER

TEST

LIMITS

UNIT

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNIT

Input low voltage

0.5

0.2 V

0.05

Input high voltage (ports 0, 1, 2, 3, EA)

0.35 V

+ 0.55

+0.5

IH1

Input high voltage, XTAL1, RST

0.7 V

+0.5

Output low voltage, ports 1, 2, 3

= 1.6 mA

0.3

OL1

Output low voltage, port 0, ALE, PSEN

6, 5

= 3.2 mA

0.4

Output high voltage, ports 1, 2, 3

= 30

0.6

OH1

Output high voltage (port 0 in external bus
mode), ALE

, PSEN

= 1.8 V

= 3.2 mA

0.7

Logical 0 input current, ports 1, 2, 3

= 0.4 V

Logical 1-to-0 transition current, ports 1, 2, 3

= 1.25 V

= 3.3 V

300

Input leakage current, port 0

0.45 V < V

0.3 V

Power supply current (see Figure 27):

See note 4

Active mode @ 1.8 V V

/ 1 MHz

0.15

0.4

Active mode @ 1.8 V V

/ 12 MHz

1.35

1.5

Active mode @ 3.3 V V

/ 12 MHz

2.70

3.7

Idle mode @ 1.8 V V

1 MHz

0.1

0.24

Idle mode @ 1.8 V V

12 MHz

0.25

0.68

Idle mode @ 3.3 V V

12 MHz

0.5

0.68

Power-down mode (see Figure 32 for

conditions)

amb

= 0

C to 70

RST

Internal reset pull-down resistor

225

Pin capacitance

(except EA)

NOTES:
1. Typical ratings are not guaranteed. The values listed are at room temperature.
2. Capacitive loading on ports 0 and 2 may cause spurious noise to be superimposed on the V

s of ALE and ports 1 and 3. The noise is due

to external bus capacitance discharging into the port 0 and port 2 pins when these pins make 1-to-0 transitions during bus operations. In
such cases, it may be desirable to qualify ALE with a Schmitt Trigger, or use an address latch with a Schmitt Trigger STROBE input. I

can

exceed these conditions provided that no single output sinks more than 5 mA and no more than two outputs exceed the test conditions.

3. Capacitive loading on ports 0 and 2 may cause the V

on ALE and PSEN to momentarily fall below the V

0.7 V specification when the

address bits are stabilizing.

4. See Figures 29 through 32 for I

test conditions.

Active mode:

= fclk *0.1 mA/MHz + 0.3 mA (1.8 V). See Figure 27

Active mode:

= fclk *0.25 mA/MHz + 0.7 mA (3.3 V)

Idle mode:

CCI

= fclk *0.04 mA/MHz + 0.2 mA

5. Load capacitance for port 0, ALE, and PSEN = 100 pF, load capacitance for all other outputs = 80 pF.
6. Under steady state (non-transient) conditions, I

must be externally limited as follows:

Maximum I

per port pin:

10 mA

Maximum I

per 8-bit port:

20 mA

Maximum total I

for all outputs:

40 mA

If I

exceeds the test condition, V

may exceed the related specification. Pins are not guaranteed to sink current greater than the listed

test conditions.

7. ALE is tested to V

OH1

, except when ALE is off then V

is the voltage specification.

8. Pin capacitance is characterized but not tested. Pin capacitance is less than 15 pF.

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

DC ELECTRICAL CHARACTERISTICS

amb

= 0

C to +70

C, V

= 3.3 V

,10%, V

= 0 V (33 MHz devices)

SYMBOL

PARAMETER

TEST

LIMITS

UNIT

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNIT

Input low voltage

0.5

0.2 V

0.05

Input high voltage (ports 0, 1, 2, 3, EA)

0.35 V

+ 0.55

+0.5

IH1

Input high voltage, XTAL1, RST

0.7 V

+0.5

Output low voltage, ports 1, 2, 3

= 1.6 mA

0.3

OL1

Output low voltage, port 0, ALE, PSEN

6, 5

= 3.2 mA

0.4

Output high voltage, ports 1, 2, 3

= 30

0.6

OH1

Output high voltage (port 0 in external bus
mode), ALE

, PSEN

= 3.2 mA

0.7

Logical 0 input current, ports 1, 2, 3

= 0.4 V

Logical 1-to-0 transition current, ports 1, 2, 3

= 1.25 V

= 3.3 V

300

Input leakage current, port 0

0.45 V < V

0.3 V

Power supply current (see Figure 27):

See note 4

Active mode @ 33 MHz

7.6

10.6

Idle mode @ 33 MHz

1.5

Power-down mode (see Figure 32 for

conditions)

amb

= 0

C to 70

RST

Internal reset pull-down resistor

225

Pin capacitance

(except EA)

NOTES:
1. Typical ratings are not guaranteed. The values listed are at room temperature.
2. Capacitive loading on ports 0 and 2 may cause spurious noise to be superimposed on the V

s of ALE and ports 1 and 3. The noise is due

can

exceed these conditions provided that no single output sinks more than 5 mA and no more than two outputs exceed the test conditions.

3. Capacitive loading on ports 0 and 2 may cause the V

on ALE and PSEN to momentarily fall below the V

0.7 V specification when the

address bits are stabilizing.

4. See Figures 29 through 32 for I

test conditions.

Active mode:

= fclk *0.3 mA/MHz + 0.7 mA. See Figure 27

Idle mode:

CCI

= fclk *0.045 mA/MHz + 0.5 mA

5. Load capacitance for port 0, ALE, and PSEN = 100 pF, load capacitance for all other outputs = 80 pF.
6. Under steady state (non-transient) conditions, I

must be externally limited as follows:

Maximum I

per port pin:

10 mA

Maximum I

per 8-bit port:

20 mA

Maximum total I

for all outputs:

40 mA

If I

exceeds the test condition, V

may exceed the related specification. Pins are not guaranteed to sink current greater than the listed

test conditions.

7. ALE is tested to V

OH1

, except when ALE is off then V

is the voltage specification.

8. Pin capacitance is characterized but not tested. Pin capacitance is less than 15 pF.

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

AC ELECTRICAL CHARACTERISTICS

amb

= 0

C to +70

C, V

= +1.8 V to +3.3 V, V

= 0 V

1, 2, 3

12 MHz CLOCK

VARIABLE CLOCK

SYMBOL

FIGURE

PARAMETER

MIN

MAX

MIN

MAX

UNIT

1/t

CLCL

Oscillator frequency

1.0

MHz

LHLL

ALE pulse width

CLCL

AVLL

Address valid to ALE low

CLCL

LLAX

Address hold after ALE low

CLCL

LLIV

ALE low to valid instruction in

150

CLCL

100

LLPL

ALE low to PSEN low

CLCL

PLPH

PSEN pulse width

142

CLCL

PLIV

PSEN low to valid instruction in

CLCL

105

PXIX

Input instruction hold after PSEN

PXIZ

Input instruction float after PSEN

CLCL

AVIV

Address to valid instruction in

207

CLCL

105

PLAZ

PSEN low to address float

Data Memory

RLRH

21, 22

RD pulse width

275

CLCL

100

WLWH

21, 22

WR pulse width

275

CLCL

100

RLDV

21, 22

RD low to valid data in

147

CLCL

165

RHDX

21, 22

Data hold after RD

RHDZ

21, 22

Data float after RD

CLCL

LLDV

21, 22

ALE low to valid data in

350

CLCL

150

AVDV

21, 22

Address to valid data in

397

CLCL

165

LLWL

21, 22

ALE low to RD or WR low

137

239

CLCL

+50

AVWL

21, 22

Address valid to WR low or RD low

122

CLCL

130

QVWX

21, 22

Data valid to WR transition

CLCL

WHQX

21, 22

Data hold after WR

CLCL

QVWH

Data valid to WR high

287

CLCL

150

RLAZ

21, 22

RD low to address float

WHLH

21, 22

RD or WR high to ALE high

103

CLCL

+40

External Clock

CHCX

High time

CLCL

CLCX

Low time

CLCL

CHCX

CLCH

Rise time

CHCL

Fall time

Shift Register

XLXL

Serial port clock cycle time

750

12t

CLCL

QVXH

Output data setup to clock rising edge

492

10t

CLCL

133

XHQX

Output data hold after clock rising edge

CLCL

117

XHDX

Input data hold after clock rising edge

XHDV

Clock rising edge to input data valid

668

10t

CLCL

165

NOTES:
1. Parameters are valid over operating temperature range unless otherwise specified.
2. Load capacitance for port 0, ALE, and PSEN = 100 pF, load capacitance for all other outputs = 80 pF.
3. Interfacing the P87CL5xX2 to devices with float times up to 45 ns is permitted. This limited bus contention will not cause damage to Port 0

drivers.

4. Parts are guaranteed to operate down to 0 Hz. When an external clock source is used, the RST pin should be held high for a minimum of

s for power-on or wakeup from power down.

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

AC ELECTRICAL CHARACTERISTICS

amb

= 0

C to +70

C V

= 3.3 V

10%, V

= 0 V

1, 2, 3

VARIABLE CLOCK

12 MHz to f

max

33 MHz CLOCK

SYMBOL

FIGURE

PARAMETER

MIN

MAX

MIN

MAX

UNIT

LHLL

ALE pulse width

CLCL

AVLL

Address valid to ALE low

CLCL

LLAX

Address hold after ALE low

CLCL

LLIV

ALE low to valid instruction in

CLCL

LLPL

ALE low to PSEN low

CLCL

PLPH

PSEN pulse width

CLCL

PLIV

PSEN low to valid instruction in

CLCL

PXIX

Input instruction hold after PSEN

PXIZ

Input instruction float after PSEN

CLCL

AVIV

Address to valid instruction in

CLCL

PLAZ

PSEN low to address float

Data Memory

RLRH

21, 22

RD pulse width

CLCL

100

WLWH

21, 22

WR pulse width

CLCL

100

RLDV

21, 22

RD low to valid data in

CLCL

RHDX

21, 22

Data hold after RD

RHDZ

21, 22

Data float after RD

CLCL

LLDV

21, 22

ALE low to valid data in

CLCL

150

AVDV

21, 22

Address to valid data in

CLCL

165

105

LLWL

21, 22

ALE low to RD or WR low

CLCL

+50

140

AVWL

21, 22

Address valid to WR low or RD low

CLCL

QVWX

21, 22

Data valid to WR transition

CLCL

WHQX

21, 22

Data hold after WR

CLCL

QVWH

Data valid to WR high

CLCL

130

RLAZ

21, 22

RD low to address float

WHLH

21, 22

RD or WR high to ALE high

CLCL

+25

External Clock

CHCX

High time

0.38t

CLCL

CLCX

Low time

0.38t

CLCL

CHCX

CLCH

Rise time

CHCL

Fall time

Shift Register

XLXL

Serial port clock cycle time

12t

CLCL

360

QVXH

Output data setup to clock rising edge

10t

CLCL

133

167

XHQX

Output data hold after clock rising edge

CLCL

XHDX

Input data hold after clock rising edge

XHDV

Clock rising edge to input data valid

10t

CLCL

165

138

NOTES:
1. Parameters are valid over operating temperature range unless otherwise specified.
2. Load capacitance for port 0, ALE, and PSEN = 100 pF, load capacitance for all other outputs = 80 pF.
3. Interfacing the P87CL5xX2 to devices with float times up to 45ns is permitted. This limited bus contention will not cause damage to Port 0

drivers.

4. Variable clock is specified for oscillator frequencies greater than 12 MHz to 33 MHz. For frequencies equal or less than 12 MHz, see 12 MHz

"AC Electrical Characteristics", page 35.

5. Parts are guaranteed to operate down to 0 Hz. When an external clock source is used, the RST pin should be held high for a minimum of

s for power-on or wakeup from power down.

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

EPROM CHARACTERISTICS

The OTP devices described in this data sheet can be programmed
by using a modified Improved Quick-Pulse Programming

algorithm. It differs from older methods in the value used for V

(programming supply voltage) and in the width and number of the
ALE/PROG pulses.

The family contains two signature bytes that can be read and used
by an EPROM programming system to identify the device. The
signature bytes identify the device as being manufactured by
Philips.

Table 8 shows the logic levels for reading the signature byte, and for
programming the program memory, the encryption table, and the
security bits. The circuit configuration and waveforms for quick-pulse
programming are shown in Figures 33 and 34. Figure 35 shows the
circuit configuration for normal program memory verification.

Quick-Pulse Programming

The setup for microcontroller quick-pulse programming is shown in
Figure 33. Note that the device is running with a 4 to 6 MHz
oscillator. The reason the oscillator needs to be running is that the
device is executing internal address and program data transfers.

The address of the EPROM location to be programmed is applied to
ports 1 and 2, as shown in Figure 33. The code byte to be
programmed into that location is applied to port 0. RST, PSEN and
pins of ports 2 and 3 specified in Table 8 are held at the `Program
Code Data' levels indicated in Table 8. The ALE/PROG is pulsed
low 5 times as shown in Figure 34.

To program the encryption table, repeat the 5 pulse programming
sequence for addresses 0 through 1FH, using the `Pgm Encryption
Table' levels. Do not forget that after the encryption table is
programmed, verification cycles will produce only encrypted data.

To program the security bits, repeat the 5 pulse programming
sequence using the `Pgm Security Bit' levels. After one security bit is
programmed, further programming of the code memory and
encryption table is disabled. However, the other security bits can still
be programmed.

Note that the EA/V

pin must not be allowed to go above the

maximum specified V

level for any amount of time. Even a narrow

glitch above that voltage can cause permanent damage to the

device. The V

source should be well regulated and free of glitches

and overshoot.

Program Verification
If security bits 2 and 3 have not been programmed, the on-chip
program memory can be read out for program verification. The
address of the program memory locations to be read is applied to
ports 1 and 2 as shown in Figure 35. The other pins are held at the
`Verify Code Data' levels indicated in Table 8. The contents of the
address location will be emitted on port 0. External pull-ups are
required on port 0 for this operation.

If the 64 byte encryption table has been programmed, the data
presented at port 0 will be the exclusive NOR of the program byte
with one of the encryption bytes. The user will have to know the
encryption table contents in order to correctly decode the verification
data. The encryption table itself cannot be read out.

Reading the Signature bytes
The signature bytes are read by the same procedure as a normal
verification of locations 030h and 031h, except that P3.6 and P3.7
need to be pulled to a logic low. The values are:
(030h) =

15h; indicates manufacturer (Philips)

(031h) =

92h -- P87CL52X2
BBH -- P87CL54X2

Program/Verify Algorithms

Any algorithm in agreement with the conditions listed in Table 8, and
which satisfies the timing specifications, is suitable.

Security Bits

With none of the security bits programmed the code in the program
memory can be verified. If the encryption table is programmed, the
code will be encrypted when verified. When only security bit 1 (see
Table 9) is programmed, MOVC instructions executed from external
program memory are disabled from fetching code bytes from the

internal memory, EA is latched on Reset and all further programming

of the EPROM is disabled. When security bits 1 and 2 are
programmed, in addition to the above, verify mode is disabled.
When all three security bits are programmed, all of the conditions
above apply and all external program memory execution is disabled.

Encryption Array

64 bytes of encryption array are initially unprogrammed (all 1s).

Trademark phrase of Intel Corporation.

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

Table 8. EPROM Programming Modes

MODE

RST

PSEN

ALE/PROG

EA/V

P2.7

P2.6

P3.7

P3.6

P3.3

Read signature

Program code data

Verify code data

Pgm encryption table

Pgm security bit 1

Pgm security bit 2

Pgm security bit 3

Program to 6-clock mode

Verify 6-clock

Verify security bits

NOTES:
1. `0' = Valid low for that pin, `1' = valid high for that pin.
2. V

= 12.75 V

0.25 V.

3. V

= 5 V

10% during programming and verification.

4. Bit is output on P0.4 (1 = 12x, 0 = 6x).
5. Security bit one is output on P0.7.

Security bit two is output on P0.6.
Security bit three is output on P0.3.

ALE/PROG receives 5 programming pulses for code data (also for user array; 5 pulses for encryption or security bits) while V

is held at

12.75 V. Each programming pulse is low for 100

s (

s) and high for a minimum of 10

Table 9. Program Security Bits for EPROM Devices

PROGRAM LOCK BITS

1, 2

SB1

SB2

SB3

PROTECTION DESCRIPTION

No Program Security features enabled. (Code verify will still be encrypted by the Encryption Array if
programmed.)

MOVC instructions executed from external program memory are disabled from fetching code bytes
from internal memory, EA is sampled and latched on Reset, and further programming of the EPROM
is disabled.

Same as 2, also verify is disabled.

Same as 3, external execution is disabled. Internal data RAM is not accessible.

NOTES:
1. P programmed. U unprogrammed.
2. Any other combination of the security bits is not defined.

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

PROGRAMMING AND VERIFICATION CHARACTERISTICS

amb

= 21

C to +27

C, V

= 5 V

10%, V

= 0 V (See Figure 36)

SYMBOL

PARAMETER

MIN

MAX

UNIT

Programming supply voltage

12.5

13.0

Programming supply current

1/t

CLCL

Oscillator frequency

MHz

AVGL

Address setup to PROG low

48t

CLCL

GHAX

Address hold after PROG

48t

CLCL

DVGL

Data setup to PROG low

48t

CLCL

GHDX

Data hold after PROG

48t

CLCL

EHSH

P2.7 (ENABLE) high to V

48t

CLCL

SHGL

setup to PROG low

GHSL

hold after PROG

GLGH

PROG width

110

AVQV

Address to data valid

48t

CLCL

ELQZ

ENABLE low to data valid

48t

CLCL

EHQZ

Data float after ENABLE

48t

CLCL

GHGL

PROG high to PROG low

NOTE:
1. Not tested.

PROGRAMMING

VERIFICATION

ADDRESS

DATA IN

DATA OUT

LOGIC 1

LOGIC 0

AVQV

EHQZ

ELQV

SHGL

GHSL

GLGH

GHGL

AVGL

GHAX

DVGL

GHDX

P1.0P1.7
P2.0P2.5

P3.4

(A0 A12)

PORT 0

P0.0 P0.7

(D0 D7)

ALE/PROG

EA/V

P2.7

SU01414

EHSH

NOTES:
*

FOR PROGRAMMING CONFIGURATION SEE FIGURE 33.

FOR VERIFICATION CONDITIONS SEE FIGURE 35.

SEE TABLE 8.

Figure 36. Programming and Verification

Philips Semiconductors

Product data

P87CL52X2/54X2

80C51 8-bit microcontroller family

8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)

2003 May 14

REVISION HISTORY

Rev

Date

Description

20030514

Product data (9397 750 11515); ECN 853-2427 29875 of 29 April 2003
Modifications:

Change to Product data

20030430

Preliminary data (9397 750 11442)

Definitions

Short-form specification -- The data in a short-form specification is extracted from a full data sheet with the same type number and title. For detailed information see
the relevant data sheet or data handbook.

Limiting values definition -- Limiting values given are in accordance with the Absolute Maximum Rating System (IEC 60134). Stress above one or more of the limiting
values may cause permanent damage to the device. These are stress ratings only and operation of the device at these or at any other conditions above those given
in the Characteristics sections of the specification is not implied. Exposure to limiting values for extended periods may affect device reliability.

Application information -- Applications that are described herein for any of these products are for illustrative purposes only. Philips Semiconductors make no
representation or warranty that such applications will be suitable for the specified use without further testing or modification.

Disclaimers

Life support -- These products are not designed for use in life support appliances, devices, or systems where malfunction of these products can reasonably be
expected to result in personal injury. Philips Semiconductors customers using or selling these products for use in such applications do so at their own risk and agree
to fully indemnify Philips Semiconductors for any damages resulting from such application.

Right to make changes -- Philips Semiconductors reserves the right to make changes in the products--including circuits, standard cells, and/or software--described
or contained herein in order to improve design and/or performance. When the product is in full production (status `Production'), relevant changes will be communicated
via a Customer Product/Process Change Notification (CPCN). Philips Semiconductors assumes no responsibility or liability for the use of any of these products, conveys
no license or title under any patent, copyright, or mask work right to these products, and makes no representations or warranties that these products are free from patent,
copyright, or mask work right infringement, unless otherwise specified.

Contact information

For additional information please visit
http://www.semiconductors.philips.com.

Fax: +31 40 27 24825

For sales offices addresses send e-mail to:
sales.addresses@www.semiconductors.philips.com.

Koninklijke Philips Electronics N.V. 2003

Date of release: 05-03

Document order number:

9397 750 11515

Philips

Semiconductors

Data sheet status

[1]

Objective data

Preliminary data

Product data

Product
status

[2] [3]

Development

Qualification

Production

Definitions

This data sheet contains data from the objective specification for product development.
Philips Semiconductors reserves the right to change the specification in any manner without notice.

This data sheet contains data from the preliminary specification. Supplementary data will be published

at a later date. Philips Semiconductors reserves the right to change the specification without notice, in

order to improve the design and supply the best possible product.

This data sheet contains data from the product specification. Philips Semiconductors reserves the

right to make changes at any time in order to improve the design, manufacturing and supply. Relevant

changes will be communicated via a Customer Product/Process Change Notification (CPCN).

Data sheet status

[1] Please consult the most recently issued data sheet before initiating or completing a design.

[2] The product status of the device(s) described in this data sheet may have changed since this data sheet was published. The latest information is available on the Internet at URL

http://www.semiconductors.philips.com.

[3] For data sheets describing multiple type numbers, the highest-level product status determines the data sheet status.

Level

III

Document Outline

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Document Outline

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