I/O PORTS S3C8245/P8245/C8249/P8249
9-10
PORT 3
Port 3 is an 5-bit I/O port with individually configurable pins. Port 3 pins are accessed directly by writing or reading
the port 3 data register, P3 at location F9H in set 1, bank 0. P3.0–P3.3 can serve as inputs (with or without pull-ups),
as push-pull outputs, or you can configure the following alternative functions:
TACAP, TACLK, TAOUT, TAPWM and TBPWM
Port 3 Control Registers
Port 3 has two 8-bit control registers: P3CONH for P3.4 and P3CONL for P3.0–P3.3. A reset clears the P3CONH
and P3CONL registers to “00H”, configuring all pins to input mode. You use control registers settings to select input
or output mode, enable pull-up resistors, and enable the alternative functions.
When programming this port, please remember that any alternative peripheral I/O function you configure using the
port 3 control registers must also be enabled in the associated peripheral module.
Port 3 Control high Register, High Byte (P3CONH)
E8H, Set 1, Bank 0, R/W
.7 .6 .5 .4 .3 .2 .1 .0MSB LSB
P3.4Not used
P3CONH bit-pair pin configuration settings:
00
01
1x
Input mode, pull-up
Output mode, push-pull
Input mode
Figure 9-10. Port 3 High-Byte Control Register (P3CONH)