M16C/62 Group DATASHEET

Bus ControlMitsubishi microcomputersM16C / 62 GroupSINGLE-CHIP 16-BIT CMOS MICROCOMPUTER(3) Read/write signalsWith a 16-bit data bus (BYTE pin =“L”), bit 2 of the processor mode register 0 (address 000416) select the_____ ________ ______ _____ ________ _________combinations of RD, BHE, and WR signals or RD, WRL, and WRH signals. With an 8-bit data bus (BYTE_____ ______ _______pin = “H”), use the combination of RD, WR, and BHE signals. (Set bit 2 of the processor mode register 0(address 000416) to “0”.) Tables 1.12.3 and 1.12.4 show the operation of these signals._____ ______ ________After a reset has been cancelled, the combination of RD, WR, and BHE signals is automatically selected._____ _________ _________When switching to the RD, WRL, and WRH combination, do not write to external memory until bit 2 of theprocessor mode register 0 (address 000416) has been set (Note).Note: Before attempting to change the contents of the processor mode register 0, set bit 1 of the protectregister (address 000A16) to “1”._____ ________ _________Table 1.12.3. Operation of RD, WRL, and WRH signalsData bus width16-bit(BYTE = “L”)RDLHHHWRLHLHLWRHHHLLStatus of external data busRead dataWrite 1 byte of data to even addressWrite 1 byte of data to odd addressWrite data to both even and odd addresses_____ ______ ________Table 1.12.4. Operation of RD, WR, and BHE signalsData bus width16-bit(BYTE = “L”)8-bit(BYTE = “H”)RD WR BHEH L LL H LH L HL H HA0HHLLH L L LL H L LH L Not used H / LL H Not used H / LStatus of external data busWrite 1 byte of data to odd addressRead 1 byte of data from odd addressWrite 1 byte of data to even addressRead 1 byte of data from even addressWrite data to both even and odd addressesRead data from both even and odd addressesWrite 1 byte of dataRead 1 byte of data(4) ALE signalThe ALE signal latches the address when accessing the multiplex bus space. Latch the address when theALE signal falls.When BYTE pin = “H”ALEWhen BYTE pin = “L”ALED0/A0 to D7/A7Address Data (Note 1)A0AddressA8 to A19Address (Note 2)D0/A1 to D7/A8Address Data (Note 1)A9 to A19AddressNote 1: Floating when reading.Note 2: When multiplexed bus for the entire space is selected, these are I/O ports.Figure 1.12.2. ALE signal and address/data bus35