Intel Microcontroller User Manual
8-2
8XC196NP, 80C196NU USER’S MANUAL
An independent, 15-bit baud-rate generator controls the baud rate of the serial port. Either the in-
ternal peripheral clock or T1CLK can provide the clock signal. The baud-rate register
(SP_BAUD) selects the clock source and the baud rate.
ternal peripheral clock or T1CLK can provide the clock signal. The baud-rate register
(SP_BAUD) selects the clock source and the baud rate.
8.2
SERIAL I/O PORT SIGNALS AND REGISTERS
Table 8-1 describes the SIO signals and Table 8-2 describes the control and status registers.
Table 8-1. Serial Port Signals
Port
Pin
Serial Port
Signal
Serial
Port
Signal
Type
Description
P2.0
TXD
O
Transmit Serial Data
In modes 1, 2, and 3, TXD transmits serial port output data. In mode 0,
it is the serial clock output.
it is the serial clock output.
P2.1
RXD
I/O
Receive Serial Data
In modes 1, 2, and 3, RXD receives serial port input data. In mode 0, it
functions as an input or an open-drain output for data.
functions as an input or an open-drain output for data.
P1.4
T1CLK
I
Timer 1 Clock
External clock source for the baud-rate generator input.
Table 8-2. Serial Port Control and Status Registers
Mnemonic
Address
Description
INT_MASK
0013H
Interrupt Mask
Setting the TI bit enables the transmit interrupt; clearing the bit
disables (masks) the interrupt.
disables (masks) the interrupt.
Setting the RI bit enables the receive interrupt; clearing the bit
disables (masks) the interrupt.
disables (masks) the interrupt.
INT_PEND
0012H
Interrupt Pending
When set, the TI bit indicates a pending transmit interrupt.
When set, the RI bit indicates a pending receive interrupt.
P1_DIR
1FD2H
Port 1 Direction
This register selects the direction of each port 1 pin. To use T1CLK
as the input clock to the baud-rate generator, clear P1_DIR.4.
as the input clock to the baud-rate generator, clear P1_DIR.4.
P1_MODE
1FD0H
Port 1 Mode
This register selects either the general-purpose input/output function
or the peripheral function for each pin of port 1. To use T1CLK as the
clock source for the baud-rate generator, set P1_MODE.4 to
configure T1CLK (P1.4) for the SIO port.
or the peripheral function for each pin of port 1. To use T1CLK as the
clock source for the baud-rate generator, set P1_MODE.4 to
configure T1CLK (P1.4) for the SIO port.