Rainbow Electronics AT89C5122 - Manual (Page 55)

55
AT8xC5122/23
4202E–SCR–06/06
Port 3 Port 3 has the following functions:
– Default function: Port 3 is an 8-bit I/O port.
– Alternate functions: see table below
Port 3 has the following configurations:
– Default configuration: Pseudo bi-directional “Port51” digital input/output with
internal pull-ups.
– Alternate configurations: See Table 32.
Table 32. Port 3 Description
Port
Alternate Functions Configurations
Signal Description Mode 1 Mode 2 Mode 3 Mode 4
P3.0 RxD
Receiver data input (asynchronous) or data input/output
(synchronous) of the serial interface
Push-pull KB_OUT Input WPU
P3.1 TxD
Transmitter data output (asynchronous) or clock output
(synchronous) of the serial interface
Push-pull KB_OUT Input WPU
P3.2 INT0 External interrupt 0 input/timer 0 gate control input LED0
P3.3 INT1 External interrupt 1input/timer 1 gate control input Push-pull KB_OUT Input WPU
P3.4 T0 Timer 0 counter input Push-pull KB_OUT Input WPU LED1
P3.5 T1 Timer 1 counter input
P3.6 WR
External Data Memory write strobe; latches the data byte
from port 0 into the external data memory
LED2
P3.7 RD
External Data Memory read strobe; Enables the external
data memory. Port 3 can drive CMOS inputs without external
pull-ups
LED3