IS80C52
IS80C32
Table 1. Detailed Pin Description
(continued)
Symbol
P3.0-P3.7
PDIP
10-17
PLCC
11, 13-19
PQFP
5, 7-13
I/O
I/O
Name and Function
ISSI
®
Port 3:
Port 3 is an 8-bit bidirectional I/O port with internal
pullups. Port 3 pins that have 1s written to them are pulled high
by the internal pullups and can be used as inputs. As inputs,
Port 3 pins that are externally pulled low will source current
because of the internal pullups. (See DC Characteristics: I
IL
).
Port 3 also serves the special features of the IS80C51/31, as
listed below:
10
11
12
13
14
15
16
17
11
13
14
15
16
17
18
19
32
5
7
8
9
10
11
12
13
26
I
O
I
I
I
I
O
O
O
PSEN
RxD (P3.0):
Serial input port.
TxD (P3.1):
Serial output port.
INT0
(P3.2):
External interrupt 0.
INT1
(P3.3):
External interrupt 1.
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.
Program Store Enable:
The read strobe to external program
memory. When the device 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.
Reset:
A high on this pin for two machine cycles while the
oscillator is running, resets the device. An internal MOS
resistor to GND permits a power-on reset using only an
external capacitor connected to Vcc.
Crystal 1:
Input to the inverting oscillator amplifier and
input to the internal clock generator circuits.
Crystal 2:
Output from the inverting oscillator amplifier.
Ground:
0V reference.
Power Supply:
This is the power supply voltage for operation.
29
RST
9
10
4
I
XTAL 1
XTAL 2
GND
Vcc
19
18
20
40
21
20
22
44
15
14
16
38
I
O
I
I
6
Integrated Silicon Solution, Inc. — 1-800-379-4774
MC004-1D
11/19/98
ISSI [ INTEGRATED SILICON SOLUTION, INC ]
