IS89C52
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 IS89C52, 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
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.
PSEN
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
MC013-1C
11/21/98
ISSI [ INTEGRATED SILICON SOLUTION, INC ]
