S93WD462/S93WD463

Characteristics subject to change without notice

Precision Supply-Voltage Monitor and Reset Controller
With a Watchdog Timer and 1k-bit Microwire Memory

SUMMIT

MICROELECTRONICS, Inc.

2029 2.2 1/23/01

FEATURES

Precision Monitor & RESET Controller

-- RESET and RESET Outputs
-- Guaranteed RESET Assertion to V

= 1V

-- 150ms Reset Pulse Width
-- Internal 1.26V Reference with ±1% Accuracy
-- ZERO External Components Required

Watchdog Timer

-- Nominal 1.6 Second Time-out Period
-- Reset by Any Transition of CS

Memory

-- 1K-bit Microwire Memory
-- S93WD462

Internally Ties ORG Low
100% Compatible With all 8-bit

Implementations

 Sixteen Byte Page Write Capability

-- S93WD463

Internally Ties ORG High
100% Compatible With all 16-bit

Implementations

 Eight Word Page Write Capability

OVERVIEW

The S93WD462 and S93WD463 are precision power
supervisory circuits providing both active high and
active low reset output. Both devices also incorporate a
watchdog timer with a nominal time-out value of 1.6
seconds.

Both devices have 1k-bits of E

PROM memory that is

accessible via the industry standard microwire bus. The
S93WD462 is configured with an internal ORG pin tied
low providing a 8-bit byte organization and the
S93WD463 is configured with an internal ORG pin tied
high providing a 16-bit word organization. Both the
S93WD462 and S93WD463 have page write capabil-
ity. The devices are designed for a minimum 100,000
program/erase cycles and have data retention in ex-
cess of 100 years.

BLOCK DIAGRAM

GND

VCC

RESET#

VTRIP

RESET
PULSE

GENERATOR

5kHz

OSCILLATOR

RESET

CONTROL

MODE

DECODE

ADDRESS

DECODER

WRITE

CONTROL

DATA I/O

E2PROM

MEMORY

ARRAY

RESET

1.26V

WATCHDOG

TIMER

2029 T BD 2.0

S93WD462/S93WD463

2029 2.2 1/23/01

SUMMIT MICROELECTRONICS, Inc.

PIN FUNCTIONS

Pin Name

Function

Chip Select

Clock Input

Serial Data Input

Serial Data Output

+2.7 to 6.0V Power Supply

GND

Ground

RESET/RESET#

RESET I/O

PIN CONFIGURATION

DEVICE OPERATION

APPLICATIONS
The S93WD462/WD463 is ideal for applications requir-
ing low voltage and low power consumption. This device
provides microcontroller RESET control and can be
manually resettable.

RESET CONTROLLER DESCRIPTION
The S93WD462/WD463 provides a precision reset con-
troller that ensures correct system operation during
brownout and power-up/-down conditions. It is config-
ured with two open drain reset outputs; pin 7 is an active
high output and pin 6 is an active low output.

During power-up, the reset outputs remain active until
V

reaches the V

TRIP

threshold. The outputs will con-

tinue to be driven for approximately 150ms after reaching

TRIP

. The reset outputs will be valid so long as V

1.0V. During power-down, the reset outputs will begin
driving active when V

falls below V

TRIP

The reset pins are I/Os; therefore, the S93WD462/
WD463 can act as a signal conditioning circuit for an
externally applied reset. The inputs are edge triggered;
that is, the RESET input will initiate a reset time-out after
detecting a low to high transition and the RESET# input
will initiate a reset time-out after detecting a high to low
transition. Refer to the applications Information section
for more details on device operation as a debounce/
reset extender circuit.

It should be noted the reset outputs are open drain. When
used as outputs driving a circuit they need to be either
tied high (

RESET#

) or tied to ground (RESET) through

the use of pull-up or pull-down resistors. Refer to the
applications aid section for help in determining the value
of resistor to be used. Internally these pins are weakly
pulled up (

RESET#

) and pulled down (RESET): there-

fore, if the signals are not being used the pins may be left
unconnected.

WATCHDOG TIMER DESCRIPTION
The S93WD462/WD463 has a watchdog timer with a
nominal time-out period of 1.6 seconds. Whenever the
watchdog times out, it will generate a reset output to both
pins 6 and 7. The watchdog timer is reset by any
transition on CS.

The watchdog timer will be held in a reset state during
power-on while V

is less than V

TRIP

. Once V

exceeds V

TRIP

the watchdog will continue to be held in

a reset state for the t

PURST

period. After t

PURST

it will be

released and the timer will begin operation. If either reset
input is asserted the watchdog timer will be reset and
remain in the reset condition until either t

PURST

has

expired or the reset input is released, whichever is
longer.

GENERAL OPERATION
The S93WD462/WD463 is a 1024-bit nonvolatile memory
intended for use with industry standard microproces-
sors. The S93WD463 is organized as X16, seven 9-bit
instructions control the reading, writing and erase
operations of the device. The S93WD462 is organized
as X8, seven 10-bit instructions control the reading,
writing and erase operations of the device. The device
operates on a single 3V or 5V supply and will generate on
chip, the high voltage required during any write opera-
tion.

CS
SK

VCC
RESET
RESET#
GND

1
2
3
4

8
7
6
5

8-Pin PDIP

or 8-Pin SOIC

2029 T PCon 2.0

S93WD462/S93WD463

2029 2.2 1/23/01

SUMMIT MICROELECTRONICS, Inc.

Instructions, addresses, and write data are clocked into
the DI pin on the rising edge of the clock (SK). The DO
pin is normally in a high impedance state except when
reading data from the device, or when checking the
ready/busy status after a write operation.

The ready/busy status can be determined after the start
of a write operation by selecting the device (CS high)
and polling the DO pin; DO low indicates that the write
operation is not completed, while DO high indicates that
the device is ready for the next instruction. See the
Applications Aid section for detailed use of the ready
busy status.

The format for all instructions is: one start bit; two op
code bits and either six (x16) or seven (x8) address or
instruction bits.

Read
Upon receiving a READ command and an address
(clocked into the DI pin), the DO pin of the S93WD462/
WD463 will come out of the high impedance state and,
will first output an initial dummy zero bit, then begin
shifting out the data addressed (MSB first). The output
data bits will toggle on the rising edge of the SK clock and
are stable after the specified time delay
(t

PD0

or t

PD1

Write
After receiving a WRITE command, address and the
data, the CS (Chip Select) pin must be deselected for a
minimum of 250ns (t

CSMIN

). The falling edge of CS will

start automatic erase and write cycle to the memory
location specified in the instruction. The ready/busy
status of the S93WD462/WD463 can be determined by
selecting the device and polling the DO pin.

Figure 1. Sychronous Data Timing

Figure 2. Read Instruction Timing

2029 ILL 3.0

t DIS

PD0,

PD1

tCSMIN

tCSS

tDIS

tDIH

tSKHI

t CSH

VALID

DATA V ALID

t SKLOW

2029 ILL4.0

tCS

STANDBY

tHZ

HIGH-Z

AN AN1

DN DN1

tPD0

S93WD462/S93WD463

2029 2.2 1/23/01

SUMMIT MICROELECTRONICS, Inc.

Erase
Upon receiving an ERASE command and address, the
CS (Chip Select) pin must be deselected for a minimum
of 250ns (t

CSMIN

). The falling edge of CS will start the

auto erase cycle of the selected memory location. The
ready/busy status of the S93WD462/WD463 can be
determined by selecting the device and polling the DO
pin. Once cleared, the content of a cleared location
returns to a logical "1" state.

Erase/Write Enable and Disable
The S93WD462/WD463 powers up in the write disable
state. Any writing after power-up or after an EWDS
(write disable) instruction must first be preceded by the
EWEN (write enable) instruction. Once the write in-
struction is enabled, it will remain enabled until power to
the device is removed, or the EWDS instruction is sent.
The EWDS instruction can be used to disable all
S93WD462/WD463 write and clear instructions, and
will prevent any accidental writing or clearing of the
device. Data can be read normally from the device
regardless of the write enable/disable status.

Page Write
93WD462 - Assume WEN has been issued. The host
will then take CS high, and begin clocking in the start
bit, write command and 7-bit address immediately
followed by the first byte of data to be written. The host
can then continue clocking in 8-bit bytes of data with
each byte to be written to the next higher address.
Internally the address pointer is incremented after
receiving each group of eight clocks; however, once
the address counter reaches xxx 1111 it will roll over
to xxx 0000 with the next clock. After the last bit is
clocked in no internal write operation will occur until CS
is brought low.

93WD463 - Assume WEN has been issued. The host
will then take CS high, and begin clocking in the start
bit, write command and 6-bit address immediately
followed by the first 16-bit word of data to be written.
The host can then continue clocking in 16-bit words of
data with each word to be written to the next higher

address. Internally the address pointer is incremented
after receiving each group of sixteen clocks; however,
once the address counter reaches xxx x111 it will roll
over to xx x000 with the next clock. After the last bit is
clocked in no internal write operation will occur until CS
is brought low.

Continuous Read
This begins just like a standard read with the host
issuing a read instruction and clocking out the data
byte [word]. If the host then keeps CS high and
continues generating clocks on SK, the S93WD462/
WD463 will output data from the next higher address
location. The S93WD462/WD463 will continue
incrementing the address and outputting data so long
as CS stays high. If the highest address is reached, the
address counter will roll over to address 0000. CS
going low will reset the instruction register and any
subsequent read must be initiated in the normal man-
ner of issuing the command and address.

Erase All
Upon receiving an ERAL command, the CS (Chip Se-
lect) pin must be deselected for a minimum of 250ns
(t

CSMIN

). The falling edge of CS will start the self clocking

clear cycle of all memory locations in the device. The
clocking of the SK pin is not necessary after the device
has entered the self clocking mode. The ready/busy
status of the S93WD462/WD463 can be determined by
selecting the device and polling the DO pin. Once
cleared, the contents of all memory bits will be in a
logical "1" state.

Write All
Upon receiving a WRAL command and data, the CS
(Chip Select) pin must be deselected for a minimum of
250ns (t

CSMIN

). The falling edge of CS will start the self

clocking data write to all memory locations in the device.
The clocking of the SK pin is not necessary after the
device has entered the self clocking mode. The ready/
busy status of the S93WD462/WD463 can be deter-
mined by selecting the device and polling the DO pin. It
is not necessary for all memory locations to be cleared
before the WRAL command is executed.

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