TS80C31X2
6.3 TS80C31X2 Serial I/O Port
The serial I/O port in the TS80C31X2 is compatible with the serial I/O port in the 80C31.
It provides both synchronous and asynchronous communication modes. It operates as an Universal Asynchronous
Receiver and Transmitter (UART) in three full-duplex modes (Modes 1, 2 and 3). Asynchronous transmission and
reception can occur simultaneously and at different baud rates
Serial I/O port includes the following enhancements:
q
q
Framing error detection
Automatic address recognition
6.3.1 Framing Error Detection
Framing bit error detection is provided for the three asynchronous modes (modes 1, 2 and 3). To enable the framing
bit error detection feature, set SMOD0 bit in PCON register (See Figure 4).
SM0/FE SM1
SM2
REN
TB8
RB8
TI
RI
SCON (98h)
Set FE bit if stop bit is 0 (framing error) (SMOD = 1)
SM0 to UART mode control (SMOD = 0)
SMOD1 SMOD0
-
POF
GF1
GF0
PD
IDL
PCON (87h)
To UART framing error control
Figure 4. Framing Error Block Diagram
When this feature is enabled, the receiver checks each incoming data frame for a valid stop bit. An invalid stop
bit may result from noise on the serial lines or from simultaneous transmission by two CPUs. If a valid stop bit
is not found, the Framing Error bit (FE) in SCON register (See Table 5.) bit is set.
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Rev. A - Mar. 19, 1999
Preliminary