SyncMOS Technologies International, Inc.
1.3 I/O Pin Configuration
SM89516A
8-Bits Micro-controller
With 64KB flash & 1KB RAM embedded
The ports 1, 2 and 3 of standard 8051 have internal pull-up resistor, and port 0 has open-drain outputs. Each I/O pin
can be used independently as an input or an output. For I/O ports to be used as an input pin, the port bit latch must
contain a ‘1’ which turns off the output driver FET. Then for port 1, 2 and 3 port pin is pulled high by a weak internal
pull-up, and can be pulled low by an external source. The port 0 has open-drain outputs which means its pull-ups are
not active during normal port operation. Writing ‘1’ to the port 0 bit latch will causing bit floating so that it can be used as
a high-impedance input.
The port 4 used as GPIO will has the same function as port 1, 2 and 3.
2. Port 4 for PLCC or QFP package :
The bit addressable port 4 is available with PLCC or QFP package. The port 4 has only 4 pins and its port address is
located at 0D8H. The function of port 4 is the same as the function of port 1, port 2 and port 3.
Port4 (P4, $D8)
bit-7
Unused
Read / Write:
Reset value:
-
*
Unused
-
*
Unused
-
*
Unused
-
*
P4.3
R/W
1
P4.2
R/W
1
P4.1
R/W
1
bit-0
P4.0
R/W
1
The bit 3, bit 2, bit 1, bit 0 output the setting to pin P4.3, P4.2, P4.1, P4.0 respectively.
The port 4 output buffers can sink 20mA and can drive LED display directly.
Specifications subject to change without notice contact your sales representatives for the most recent information.
Ver 2.1 SM89516A 08/2006
8
SYNCMOS [ SYNCMOS TECHNOLOGIES,INC ]
