M16C User Manual.pdf

Clock synchronous serial I/O modeMitsubishi microcomputersM16C / 62 GroupSINGLE-CHIP 16-BIT CMOS MICROCOMPUTER(1) Clock synchronous serial I/O modeThe clock synchronous serial I/O mode uses a transfer clock to transmit and receive data. Tables 1.19.2and 1.19.3 list the specifications of the clock synchronous serial I/O mode. Figure 1.19.9 shows theUARTi transmit/receive mode register.Table 1.19.2. Specifications of clock synchronous serial I/O mode (1)ItemSpecificationTransfer data format • Transfer data length: 8 bitsTransfer clock • When internal clock is selected (bit 3 at addresses 03A016, 03A816, 037816= “0”) : fi/ 2(n+1) (Note 1) fi = f1, f8, f32• When external clock is selected (bit 3 at addresses 03A016, 03A816, 037816= “1”) : Input from CLKi pin_______ _______ _______ _______Transmission/reception control • CTS function/RTS function/CTS, RTS function chosen to be invalidTransmission start condition • To start transmission, the following requirements must be met:_ Transmit enable bit (bit 0 at addresses 03A516, 03AD16, 037D16) = “1”_ Transmit buffer empty flag (bit 1 at addresses 03A516, 03AD16, 037D16) = “0”_______________ When CTS function selected, CTS input level = “L”• Furthermore, if external clock is selected, the following requirements must also be met:_ CLKi polarity select bit (bit 6 at addresses 03A416, 03AC16, 037C16) = “0”:CLKi input level = “H”_ CLKi polarity select bit (bit 6 at addresses 03A416, 03AC16, 037C16) = “1”:CLKi input level = “L”Reception start condition • To start reception, the following requirements must be met:_ Receive enable bit (bit 2 at addresses 03A516, 03AD16, 037D16) = “1”_ Transmit enable bit (bit 0 at addresses 03A516, 03AD16, 037D16) = “1”_ Transmit buffer empty flag (bit 1 at addresses 03A516, 03AD16, 037D16) = “0”• Furthermore, if external clock is selected, the following requirements mustalso be met:_ CLKi polarity select bit (bit 6 at addresses 03A416, 03AC16, 037C16) = “0”:CLKi input level = “H”_ CLKi polarity select bit (bit 6 at addresses 03A416, 03AC16, 037C16) = “1”:CLKi input level = “L”Interrupt request • When transmittinggeneration timing_ Transmit interrupt cause select bit (bits 0, 1 at address 03B016, bit 4 ataddress 037D16) = “0”: Interrupts requested when data transfer from UARTitransfer buffer register to UARTi transmit register is completed_ Transmit interrupt cause select bit (bits 0, 1 at address 03B016, bit 4 ataddress 037D16) = “1”: Interrupts requested when data transmission fromUARTi transfer register is completed• When receiving_ Interrupts requested when data transfer from UARTi receive register toUARTi receive buffer register is completedError detection • Overrun error (Note 2)This error occurs when the next data is ready before contents of UARTireceive buffer register are read outNote 1: “n” denotes the value 0016 to FF16 that is set to the UART bit rate generator.Note 2: If an overrun error occurs, the UARTi receive buffer will have the next data written in. Note also thatthe UARTi receive interrupt request bit is not set to “1”.122