ML51Dec. 05, 2018 Page 201 of 401 Rev 1.00ML51 SERIES TECHNICAL REFERENCE MANUAL2. Either SM2 (SCON.5) = 0, or the received stop bit = 1 while SM2 = 1 and the received data matches“Given” or “Broadcast” address. (For enhancement function, see Section 15.7“MultiprocessorCommunication” and Section 15.8“Automatic Address Recognition”.)If these conditions are met, then the SBUF will be loaded with the received data, the RB8 (SCON.2)with stop bit, and RI will be set. If these conditions fail, there will be no data loaded and RI will remain0. After above receiving progress, the serial control will look forward another 1-to-0 transition on RXDpin to start next data reception.15.3 Mode 2Mode 2 supports asynchronous, full duplex serial communication. Different from Mode1, there are 11bits to be transmitted or received. They are a start bit (logic 0), 8 data bits (LSB first), a programmable9th bit TB8 or RB8 bit and a stop bit (logic 1). The most common use of 9th bit is to put the parity bit in itor to label address or data frame for multiprocessor communication. The baud rate is fixed as 1/32 or1/64 the system clock frequency depending on SMOD (PCON.7) bit. Figure 15.3-1 shows theassociated timings of the serial port in Mode 2 for transmitting and receiving.Figure 15.3-1 Serial Port Mode 2 and 3 Timing DiagramTransmission is initiated by any writing instructions to SBUF. Transmission takes place on TXD pin.First the start bit comes out, the 8-bit data and bit TB8 (SCON.3) follows to be shifted out and thenends with a stop bit. After the stop bit appears, TI will be set to indicate the transmission complete.While REN is set, the reception is allowed at any time. A falling edge of a start bit on RXD will initiatethe reception progress. Data will be sampled and shifted in at the selected baud rate. In the midst ofthe stop bit, certain conditions should be met to load SBUF with the received data:
