IS89C51 Datasheet, PDF (6/48 Pages) Integrated Silicon Solution, Inc – CMOS SINGLE CHIP 8-BIT MICROCONTROLLER with 4-Kbytes of FLASH

IS89C51
ISSI ^®
Table 1. Detailed Pin Description (continued)
Symbol PDIP
P3.0-P3.7 10-17
PLCC
PQFP I/O
11, 13-19 5, 7-13 I/O
10
11
5
I
11
13
7
O
12
14
8
I
13
15
9
I
14
16
10
I
15
17
11
I
16
18
12
O
17
19
13
O
PSEN
29
32
26
O
RST
9
10
4
I
XTAL 1
19
21
15
I
XTAL 2
18
20
14
O
GND
20
22
16
I
Vcc
40
44
38
I
Name and Function
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: IIL).
Port 3 also serves the special features of the IS89C51, as listed
below:
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.
6
1-800-379-4774 — Integrated Silicon Solution, Inc.
MC016-1C
11/21/98