IS80C51
IS80C31
IS80C51
IS80C31
CMOS SINGLE CHIP
8-BIT MICROCONTROLLER
ISSI
GENERAL DESCRIPTION
ISSI
®
®
NOVEMBER 1998
FEATURES
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80C51 based architecture
4K x 8 ROM (IS80C51 only)
128 x 8 RAM
Two 16-bit Timer/Counters
Full duplex serial channel
Boolean processor
Four 8-bit I/O ports, 32 I/O lines
Memory addressing capability
– 64K ROM and 64K RAM
Power save modes:
– Idle and power-down
Six interrupt sources
Most instructions execute in 0.3
µs
CMOS and TTL compatible
Maximum speed: 40 MHz @ Vcc = 5V
Industrial temperature available
Packages available:
– 40-pin DIP
– 44-pin PLCC
– 44-pin PQFP
The
ISSI
IS80C51 and IS80C31 are high-performance
microcontrollers fabricated using high-density CMOS
technology. The CMOS IS80C51/31 is functionally
compatible with the industry standard 80C51
microcontrollers.
The IS80C51/31 is designed with 4K x 8 ROM (IS80C51
only); 128 x 8 RAM; 32 programmable I/O lines; a serial
I/O port for either multiprocessor communications, I/O
expansion or full duplex UART; two 16-bit timer/counters;
a six-source, two-priority-level, nested interrupt structure;
and an on-chip oscillator and clock circuit. The
IS80C51/31 can be expanded using standard TTL
compatible memory.
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
RST
RxD/P3.0
TxD/P3.1
INT0/P3.2
INT1/P3.3
T0/P3.4
T1/P3.5
WR/P3.6
RD/P3.7
XTAL2
XTAL1
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
VCC
P0.0/AD0
P0.1/AD1
P0.2/AD2
P0.3/AD3
P0.4/AD4
P0.5/AD5
P0.6/AD6
P0.7/AD7
EA/VPP
ALE/PROG
PSEN
P2.7/A15
P2.6/A14
P2.5/A13
P2.4/A12
P2.3/A11
P2.2/A10
P2.1/A9
P2.0/A8
Figure 1. IS80C51/31 Pin Configuration: 40-pin PDIP
ISSI reserves the right to make changes to its products at any time without notice in order to improve design and supply the best possible product. We assume no responsibility for any errors which
may appear in this publication. © Copyright 1998, Integrated Silicon Solution, Inc.
Integrated Silicon Solution, Inc. — 1-800-379-4774
MC003-1D
11/19/98
1
IS80C51
IS80C31
Table 1. Detailed Pin Description
Symbol
ALE
PDIP
30
PLCC
33
PQFP
27
I/O
I/O
Name and Function
ISSI
®
Address Latch Enable:
Output pulse for latching the low byte
of the address during an address to the 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.
External Access enable:
EA
must be externally held low to
enable the device to fetch code from external program memory
locations 0000H to FFFFH. If
EA
is held high, the device
executes from internal program memory unless the program
counter contains an address greater than 0FFFH.
Port 0:
Port 0 is an 8-bit open-drain, bidirectional I/O port. 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 pullups
when emitting 1s.
Port 1:
Port 1 is an 8-bit bidirectional I/O port with internal
pullups. Port 1 pins that have 1s written to them are pulled high
by the internal pullups and can be used as inputs. As inputs,
Port 1 pins that are externally pulled low will source current
because of the internal pullups. (See DC Characteristics: I
IL
).
The Port 1 output buffers can sink/source four TTL inputs.
Port 1 also receives the low-order address byte during ROM
verification.
EA
31
35
29
I
P0.0-P0.7
39-32
43-36
37-30
I/O
P1.0-P1.7
1-8
2-9
40-44
1-3
I/O
P2.0-P2.7
21-28
24-31
18-25
I/O
Port 2:
Port 2 is an 8-bit bidirectional I/O port with internal
pullups. Port 2 pins that have 1s written to them are pulled high
by the internal pullups and can be used as inputs. As inputs,
Port 2 pins that are externally pulled low will source current
because of the internal pullups. (See DC Characteristics: I
IL
).
Port 2 emits the high order address byte during fetches from
external program memory and during accesses to external data
memory that used 16-bit addresses (MOVX @ DPTR). In this
application, Port 2 uses strong internal pullups when emitting
1s. During accesses to external data memory that use 8-bit
addresses (MOVX @ Ri [i = 0, 1]), Port 2 emits the contents of
the P2 Special Function Register.
Port 2 also receives the high-order bits and some control
signals during ROM verification.
Integrated Silicon Solution, Inc. — 1-800-379-4774
MC003-1D
11/19/98
5
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