80C186EB/80C188EB Microprocessor User's Manual - CEUNES

SERIAL COMMUNICATIONS UNIT5. At the end of the communication, the target slave switches back to Mode 2 and waits foranother address.The parity feature cannot be used when implementing multiprocessor communications withModes 2 and 3, as the ninth data bit is a control bit and cannot be used as the parity bit.10.1.2 Synchronous CommunicationsThe synchronous mode (Mode 0) is useful primarily with shift register-based peripheral devices.The device outputs a synchronizing clock on TXD and transmits and receives data on RXD in 8-bit frames (Figure 10-7). The serial port always provides the synchronizing clock; it can neverreceive a synchronous clock on TXD. Communication in the synchronous mode is half-duplex.The RXD pin cannot transmit and receive data at the same time. Because the serial port alwaysacts as the master in Mode 0, all transmissions and receptions are controlled by the serial port. InMode 0, the parity functions and break character detection functions are not available.TXDRXD Bit 0 Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7Mode 0 TransmitTXDRXDBit 0Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7Mode 0 ReceiveA1289-0AFigure 10-7. Mode 0 Waveforms10-8