EM78451
MASK ROM
This specification is subject to change without prior notice.
2002/03/01
1
1. GENERAL DESCRIPTION
The EM78451 is an 8-bit microprocessor designed and developed with low-power and high speed CMOS
technology. Its operation kernel is implemented with RISC-like architecture. and is available in the mask
ROM version. This device is equipped with the Serial Peripheral Interface (SPI) function and an
easy-implemented RS-232. The EM78451 is very suitable for the wired communication. Only 58
easy-to-learn instructions are needed and the user's program can be emulated with EMC In-Circuit
Emulator (ICE).
EM78451
MASK ROM
This specification is subject to change without prior notice.
2002/03/01
2
2. FEATURES
Operating voltage range: 2.3V~5.5V.
Operating temperature range: 0
C~70
C.
Operating frequency rang (base on2 clocks ):
* Crystal mode: DC~20MHz at 5V, DC~8MHz at 3V, DC~4MHz at 2.3V.
* RC mode: DC~4MHz at 5V, DC~4MHz at 3V, DC~4MHz at 2.3V.
Low power consumption:
* Less then 3 mA at 5V/4MHz
* Typically 10
A during sleep mode
Serial Peripheral Interface (SPI) available.
4K
13 bits on chip ROM (EM78451).
11 special function registers.
140
8 bits on chip general-purposed registers.
5 bi-directional I/O ports (35 I/O pins).
3 LED direct sinking pins with internal serial resistors.
Built-in RC oscillator with external serial resistor, 10% variation.
Built-in power-on reset.
Five stacks for subroutine nesting.
8-bit real time clock/counter (TCC) with overflow interrupt.
Two machine clocks or four machine clocks per instruction cycle.
Power down mode.
Programmable wake up from sleep circuit on I/O ports.
Programmable free running on-chip watchdog timer.
12 wake-up pins.
2 open-drain pins.
2 R-option pins.
32 programmable pull-high input pins.
Package types:
* 40 pin DIP 600mil : EM78451AP.
* 44 pin QFP
: EM78451AQ.
EM78451
MASK ROM
This specification is subject to change without prior notice.
2002/03/01
3
Four types of interrupts.
* External interrupt (/INT).
* SPI transmission completed interrupt.
* TCC overflow interrupt.
* Timer1 comparator match interrupt.
EM78451
MASK ROM
This specification is subject to change without prior notice.
2002/03/01
4
3. PIN ASSIGNMENT
2
3
4
5
6
7
8
9
1 0
1 1
1 2
1
1 3
1 4
1 5
1 6
1 7
1 8
1 9
2 0
3 9
3 8
3 7
3 6
3 5
3 4
3 3
3 2
3 1
3 0
2 9
4 0
2 8
2 7
2 6
2 5
2 4
2 3
2 2
2 1
V S S
I N T
D A T A
P 9 1
S D I / P 9 2
S D O / P 9 3
S C K / P 9 4
S S / P 9 5
C L K
P 9 0
O S C O
P 5 0
P 5 1
P 5 2
P 5 3
P 5 4
P 5 5
P 5 6
P 5 7
P 8 0
P 8 1
P 8 3
P 8 4
P 6 0
P 8 7
P 8 6
P 8 5
P 6 2
P 6 1
P 6 3
P 6 4
P 6 5
P 6 6
R - O S C I
V D D
P 7 1
P 7 2
P 6 7
P 8 2
EM78451AP/WM
P 7 0
1
2
3
4
5
6
7
8
9
1 0
1 1
12
13
14
15
16
17
18
19
20
21
22
44
43
42
41
40
39
38
37
36
35
34
P55
P56
P86
P85
P84
P83
P82
NC
P81
P80
P57
3 3
3 2
3 1
3 0
2 9
2 8
2 7
2 6
2 5
2 4
2 3
P 8 7
P 6 4
P 6 3
P 7 2
P 6 5
P 6 6
P 6 0
P 6 1
P 6 2
P 6 7
P 7 1
P 9 0
P 9 1
S D I / P 9 2
S D O / P 9 3
P 5 0
P 5 1
P 5 2
P 5 3
P 5 4
S C K / P 9 4
S S / P 9 5
DATA
CLK
VSS
OSCO
R-OSCI
VDD
NC
NC
NC
INT
E M 7 8 4 5 1 A Q
P70
Fig. 1 Pin assignment
Table 1 Pin description
Symbol
Pin No.
Type
Function Description
R-OSCI
39
I
* In XTAL mode: Crystal input; In internal C, external R mode: 56K
ohm
5% pull high for 1.8432MHz.
OSCO
40
O
* In XTAL mode: Crystal output; In RC mode: Instruction clock output.
P90~P95
5~10
I/O
* General bi-directional I/O port. All of its pins can be pulled-high by
software.
* P90 and P91 are pin-change wake up pins.
P80~P87
19~26
I/O
* General bi-directional I/O port. All of its pins can be pulled-high by
software.
* P80 and P81 are also used as the R-option pins.
P70~P72
37~35
I/O
* LED direct-driving pin with internal serial resistor is used as output and is
software defined.
CLK
4
I/O
* By connecting P74 and P76 together.
* P74 can be pulled-high by software and it is also a pin-change wake up
pin.
* P76 can be defined as an open-drain output.
DATA
3
I/O
* By connecting P75 and P77 together.
* P75 can be pulled-high by software and it is also a pin-change wake up
pin.
* P77 can be defined as an open-drain output.
P60~P67
27~34
I/O
* General bi-directional port. All of its pins can be pulled-high by software,
and pin-change wake up pins.
P50~P57
11~18
I/O
* General bi-directional I/O port. All of its pins can be pulled-high * *
EM78451
MASK ROM
This specification is subject to change without prior notice.
2002/03/01
5
Individually by software.
VDD
38
-
* Power supply pin.
VSS
1
-
* Ground pin.
/INT
2
I
* An interrupt schmitt-triggered pin. The function of interrupt triggers at the
falling edge. Users can enable it by software. The internal pull-up resistor
is around 50K ohm.
SDI
7
I/O
* Serial data in for SPI
SDO
8
I/O
* Serial data out for SPI.
SCK
9
I/O
* Serial clock for SPI.
/SS
10
I/O
* /Slave select for SPI.
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