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I/O PORTS S3C84E5/C84E9/P84E9
9-12
PORT 3
Port 3 is an 8-bit I/O port that can be used for general-purpose digital I/O. The pins are accessed directly by writing
or reading the port 3 data register, P3 at location E3H in set 1, bank 0. P3.0–P3.7 can serve as inputs, outputs
(push pull) or you can configure the following alternative functions:
— General-purpose digital I/O
— Alternative function: ADC0– ADC7
Port 3 Control Register (P3CONH, P3CONL)
Port 3 has two 8-bit control registers: P3CONH for P3.4–P3.7 and P3CONL for P3.0–P3.3. A reset clears the
P2CONH and P2CONL registers to “00H”, configuring all pins to input mode. You use control registers settings to
select input or output mode (push-pull) and enable the alternative functions.
When programming the 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 Register, High Byte (P3CONH)
EEH, Set1, Bank0, R/W, Reset value="00"
.7 .6 .5 .4 .3 .2 .1 .0MSB LSB
[.7-.6] P3.7/ADC7 Configuration Bits
0 0 = Input mode with pull-up
0 1 = Input mode
1 0 = Push-pull output mode
1 1 = Alternative function mode: ADC7 input
[.5-.4] P3.6/ADC6 Configuration Bits
0 0 = Input mode with pull-up
0 1 = Input mode
1 0 = Push-pull output mode
1 1 = Alternative function mode: ADC6 input
[.3-.2] P3.5/ADC5 Configuration Bits
0 0 = Input mode with pull-up
0 1 = Input mode
1 0 = Push-pull output mode
1 1 = Alternative function mode: ADC5 input
[.1-.0] P3.4/ADC4 Configuration Bits
0 0 = Input mode with pull-up
0 1 = Input mode
1 0 = Push-pull output mode
1 1 = Alternative function mode: ADC4 input
Figure 9-9. Port 3 High-Byte Control Register (P3CONH)