M16C User Manual.pdf

External BusesMitsubishi microcomputersM16C / 62 GroupSINGLE-CHIP 16-BIT CMOS MICROCOMPUTER5.2 Data Access5.2.1 Data Bus WidthIf the voltage level input to the BYTE pin is “H”, the external data bus width becomes 8 bits, and P10 (/D8) through P17 (/D15) can be used as I/O ports (Figure 5.2.1).If the voltage level input to the BYTE pin is “L”, the external data bus width becomes 16 bits, and P10(/D8) through P17 (/D15) operate as a data bus (D8 through D15) (Figure 5.2.1).Bus width : 8-bit (BYTE = “H”)MicrocomputerExternal deviceP00 to P07Data bus D0 to D7P10 to P17P20 to P27P30 to P37I/O portAddress bus A0 to A15P40 to P43Address bus A16 to A19 (Note 1)P44 to P47Chip select CS0 to CS3 (Note 2)P50 to P52RD, WRL, WRH / RD, BHE, WR (Note 3)P53 to P57BCLK, HLDA, HOLD, ALE, RDYBus width : 16-bit (BYTE = “L”)MicrocomputerExternal deviceP00 to P07Data bus D0 to D7P10 to P17Data bus D8 to D15P20 to P27P30 to P37Address bus A0 to A15P40 to P43Address bus A16 to A19 (Note 1)P44 to P47Chip select CS0 to CS3 (Note 2)P50 to P52RD, WRL, WRH / RD, BHE, WR (Note 3)P53 to P57BCLK, HLDA, HOLD, ALE, RDYNote 1: Can be switched to I/O port using the port P40 to P43 function select bits of processor mode register 0 (address 000416).Note 2: When reset, only CS0 outputs a chip select signal. CS1 through CS3 become input ports.I/O ports can be switched using the CSi output enable bit of the chip select control register (address 000816).Note 3: The feature can be switched using the R/W mode select bit of processor mode register 0 (address 000416).Figure 5.2.1. Level of BYTE pin and external data bus width509