Samsung C8278X User Manual

 

 

 

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 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. 

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