Rainbow Electronics T89C51CC02 - Manual (Page 45)

Rev.A - May 17, 2001 45
Preliminary
T89C51CC02
11. Serial I/O Port
The T89C51CC02 I/O serial port is compatible with the I/O serial port in the 80C52.
It provides both synchronous and asynchronous communication modes. It operates as a 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:
•
Framing error detection
•
Automatic address recognition
Figure 25. Serial I/O Port Block Diagram
11.1. Framing Error Detection
Framing bit error detection is provided for the three asynchronous modes. To enable the framing bit error detection
feature, set SMOD0 bit in PCON register.
Figure 26. 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 bit is set.
Write SBUF
RI TI
SBUF
Transmitter
SBUF
Receiver
IB Bus
Mode 0 Transmit
Receive
Shift register
Load SBUF
Read SBUF
SCON
Interrupt Request
Serial Port
TXD
RXD
RI TI RB8 TB8 REN SM2 SM1 SM0/FE
IDL PD GF0 GF1 POF - SMOD0 SMOD1
To UART framing error control
SM0 to UART mode control
Set FE bit if stop bit is 0 (framing error)