M16C User Manual.pdf

SI/O3, 4Mitsubishi microcomputersM16C / 62 GroupSINGLE-CHIP 16-BIT CMOS MICROCOMPUTER2.6 SI/O3, 42.6.1 OverviewSI/O3, 4 carries out 8-bit data communications in synchronization with the clock. The following is anoverview of the SI/O3, 4.(1) Transmission/reception format8-bit data(2) Transfer rateIf the internal clock is selected as the transfer clock, the divide-by-2 frequency, resulting from the bitrate generator division, becomes the transfer rate. The bit rate generator count source can be selectedfrom the following: f1, f8, and f32. Clocks f1, f8, and f32 are derived by dividing the CPU’s mainclock by 1, 8, and 32 respectively.Furthermore, if an external clock is selected as the transfer clock, the clock frequency input to the CLKpin becomes the transfer rate.(3) Function selectionFor SI/O3, 4, the following functions can be selected:(a) Function for choosing which bit to transmit firstThis function is to choose whether to transmit data from bit 0 or from bit 7. Choose either of thefollowing:• LSB first Data is transmitted from bit 0.• MSB first Data is transmitted from bit 7.(b) Choosing output level when not transferring• Internal clock High-impedance output.• External clock "H" or "L" output level is selected.(6) Input to the serial I/O and the direction registerTo input an external signal to the serial I/O, set the direction register of the relevant port to input.(7) Pins related to the SI/O3, 4• CLK3, CLK4 pins Input/output pins for the transfer clock• SIN3, SIN4 pins Input pins for data• SOUT3, SOUT4 pins Output pins for data(8) Registers related to the SI/O3, 4Figure 2.6.1 shows the memory map of SI/O3, 4-related registers, and Figures 2.6.2 show SI/O3, 4-related registers.004816004916036016036116036216036316036416036516036616036716SI/O4 interrupt control register (S4IC)SI/O3 interrupt control register (S3IC)SI/O3 transmit/receive register (S3TRR)SI/O3 transmit/receive control register (S3C)SI/O3 bit rate generator (S3BRG)SI/O4 transmit/receive register (S4TRR)SI/O4 control register (S4C)SI/O4 bit rate generator (S4BRG)Figure 2.6.1. Memory map of serial I/O3, 4-related registers378