Rainbow Electronics T89C5121 - Manual (Page 6)

6
A/T8xC5121
4164G–SCR–07/06
P3.0 RxD EV
CC
I
UART function
Receive data input
I/O
Input/Output function
P3.0 is a bi-directional I/O port with internal pull-ups.
I
Reset configuration
Input (high level)
P3.1 TxD EV
CC
O
UART function
Transmit data output
OE active at low or high level depending of PMSOEN bits in SIOCON Reg.
I/O
Input/Output function
P3.1 is a bi-directional I/O port with internal pull-ups.
Z
Reset configuration
High impedance due to PMOS switched OFF
P3.2 INT0 DV
CC
I
External interrupt 0
INT0 input set IE0 in the TCON register. If bit IT0 in this register is set, bits IE0
are set by a falling edge on INT0. If bit IT0 is cleared, bits IE0 is set by a low
level on INT0.
I/O
Input/Output function
P3.2 is a bi-directional I/O port with internal pull-ups.
I
Timer 0: Gate input
INT0 serves as external run control for Timer 0 when
selected in TCON register.
I
Reset configuration
Input (high level)
P3.3 INT1 OE EV
CC
I
External Interrupt 1
INT1 input set OEIT in ISEL Register, IE1 in the TCON register.
If bit IT1 in this register is set, bits OEIT and IE1 are set by a falling edge on
INT1. If bit IT1 is cleared, bits OEIT and IE1 is set by a low level on INT1
I
UART function
Output enable. A low or high level (depending OELEV bit in
ISEL Register) on this pin disables the PMOS transistors of TxD
(P3.1) and T0 (P3.4). This function can be disabled by software
I/O
Input/Output function
P3.3 is a bi-directional I/O port with internal pull-ups.
I
Timer 1 function: Gate input
INT1 serves as external run control for Timer 1 when
selected in TCON register.
I
Reset configuration
Input (high level)
P3.4 T0 EV
CC
O
UART function
OE active at low or high level depending of PMSOEN
bits in SIOCON Reg.
Table 1. Ports Description (Continued)
Port
Signal
Name Alternate
Internal
Power
Supply ESD Type Description