Samsung S3C8275X - Manual (Page 248)

S3C8275X/F8275X/C8278X/F8278X/C8274X/F8274X I/O PORTS
9-13
PORT 3
Port 3 is an 8-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 F3H in set 1, bank 0. P3.0-P3.7 can serve as inputs (with or without pull-
up), as outputs (push-pull or open-drain) or you can be configured the following functions.
• Low-nibble pins (P3.0-P3.3): SEG23-SEG20
• High-nibble pins (P3.4-P3.7): SEG19-SEG16
Port 3 Control Registers (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
P3CONH and P3CONL registers to "00H", configuring all pins to input mode. You use control registers setting to
select input or output mode (push-pull or open-drain) 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 Pull-up Resistor Control Register (P3PUR)
Using the port 3 pull-up resistor control register, P3PUR (EFH, set 1, bank 0), you can configure pull-up resistors
to individually port 3 pins.
Port 3 Control Register, High Byte (P3CONH)
EDH, Set 1, Bank 0, R/W
.7 .6 .5 .4 .3 .2 .1 .0 MSB LSB
P3.5/SEG18 P3.4/SEG19
P3CONH bit-pair pin configuration settings:
00
01
10
11 Alternative fumction (SEG16-SEG19)
Input mode
N-channel open-drain output mode
Push-pull output mode
P3.6/SEG17 P3.7/SEG16
Figure 9-16. Port 3 High Byte Control Register (P3CONH)