SM89516B
8-Bit Micro-controller
64KB Flash
& 1KB RAM embedded
The serial port is full duplex, can transmit and receive simultaneously. The serial port receive and transmit share
the same SFR – SBUF, but actually there is two SBUF in the chip, one is for transmit and the other is for receive.
The serial port can be operated in 4 different modes.
8.1.1
Mode 0
Pin RXD serves as input and output. TXD outputs the shift clock. 8 bits are transmitted with LSB first. The baud
rate is fixed at 1/12 of the crystal frequency. Reception is initialized in Mode 0 by setting the flags in SCON as
follows: RI = 0 and REN = 1. In other modes, a start bit when REN = 1 starts receiving serial data. As shown in Fig.
Fig. 8-1: Transmit mode 0
Fig. 8-2: Receive mode 0
8.1.2
Mode 1
Pin RXD serves as input, and TXD serves as serial output. No external shift clock is used, 10 bits are transmitted: a
start bit (always 0), 8 data bits (LSB first), and a stop bit (always 1). On receive, a start bit synchronizes the
transmission, 8 data bits are available by reading SBUF, and stop bit sets the flag RB8 in the Special Function
Register SCON. In mode 1 either internal baud rate generator or timer 1 can be use to specify baud rate. As shown
in Fig. 8-3 and Fig. 8-4
Fig. 8-3: Transmit mode 1
Specifications subject to change without notice contact your sales representatives for the most recent information.
ISSFD-M087
Ver A SM89516B 3/7/2014
- 35 -
SYNCMOS [ SYNCMOS TECHNOLOGIES,INC ]
