SM39A16M1
8-Bit Micro-controller
16KB with ISP Flash
& 1K+256B RAM embedded
9.1.2 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. 9-3
and Fig. 9-4
Fig. 9-3: Transmit mode 1
Fig. 9-4: Receive mode 1
9.1.3 Mode 2
This mode is similar to Mode 1, with two differences. The baud rate is fixed at 1/32 (SMOD=1) or 1/64(SMOD=0) of
oscillator frequency and 11 bits are transmitted or received: a start bit (0), 8 data bits (LSB first), a programmable 9th
bit, and a stop bit (1). The 9th bit can be used to control the parity of the serial interface: at transmission, bit TB8 in
SCON is output as the 9th bit, and at receive, the 9th bit affects RB8 in Special Function Register SCON.
9.1.4 Mode 3
The only difference between Mode 2 and Mode 3 is that in Mode 3 either internal baud rate generator or timer 1 can be
use to specify baud rate. As shown in Fig. 9-5 and Fig. 9-6.
Fig. 9-5: Transmit modes 2 and 3
Specifications subject to change without notice contact your sales representatives for the most recent information.
ISSFD-M069
Ver C SM39A16M1 7/31/2013
- 51 -
SYNCMOS [ SYNCMOS TECHNOLOGIES,INC ]
