SM5953
8-Bit Micro-controller
15KB with ISP Flash
& 256B RAM embedded
Here Fosc is the crystal or oscillator frequency.
The serial port of Maryland 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.
8-1 and Fig. 8-2
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-M074
Ver B SM5953 12/27/2013
- 30 -
SYNCMOS [ SYNCMOS TECHNOLOGIES,INC ]
