SM5964B
8-Bit Micro-controller
64KB with ISP Flash
& 1KB RAM embedded
Fig. 8-4: Receive mode 1
8.1.3
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.
8.1.4
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. 8-5 and Fig. 8-6.
Fig. 8-5: Transmit modes 2 and 3
Fig. 8-6: Receive modes 2 and 3
8.2
Multiprocessor Communication of Serial Interface
The feature of receiving 9 bits in Modes 2 and 3 of Serial Interface can be used for multiprocessor communication.
In this case, the slave processors have bit SM2 in SCON set to 1. When the master processor outputs slave’s
address, it sets the 9th bit to 1, causing a serial port receive interrupt in all the slaves. The slave processors
compare the received byte with their network address. If there is a match, the addressed slave will clear SM2 and
receive the rest of the message, while other slaves will leave SM2 bit unaffected and ignore this message. After
addressing the slave, the host will output the rest of the message with the 9th bit set to 0, so no serial port receive
interrupt will be generated in unselected slaves.
Specifications subject to change without notice contact your sales representatives for the most recent information.
ISSFD-M081
Ver A SM5964B 3/7/2014
- 36 -
SYNCMOS [ SYNCMOS TECHNOLOGIES,INC ]
