M16C/62 Group DATASHEET

Memory Space Expansion FunctionsMitsubishi microcomputersM16C / 62 GroupSINGLE-CHIP 16-BIT CMOS MICROCOMPUTERThe data bank register is made up of the bank selection bits (bits 5 through 3) and the offset bit (bit 2). Thebank selection bits are used to set a bank number for accessing data lying between 4000016 andBFFFF16. Assigning 1 to the offset bit provides the means to set offsets covering 4000016.Figure 1.8.5 shows the memory location and chip select areas in expansion mode 2._______The area relevant to CS0 ranges from 4000016 through FFFFF16. As for the area from 4000016 through_______BFFFF16, the bank number set by use of the bank selection bits are output from the output terminals CS3_______ _______ _______- CS1 only in accessing data. In fetching a program, bank 7 (1112) is output from CS3 - CS1. As for the_______ _______area from C000016 through FFFFF16, bank 7 (1112) is output from CS3 - CS1 without regard to accessingdata or to fetching a program._______ _______ _______In accessing an area irrelevant to CS0, a chip select signal CS3 (400016 - 7FFF16), CS2 (800016 -_______27FFF16), and CS1 (2800016 - 3FFFF16) is output depending on the address as in the past.Figure 1.8.6 shows an example of connecting the MCU with a 4-M byte ROM and to a 128-K byte SRAM._______ _______ _______ _______Connect the chip select of 4-M byte ROM with CS0. Connect M16C’s CS3, CS2, and CS1 with addressinputs AD21, AD20, and AD19 respectively. Connect M16C’s output A19 with address input AD18. Figure1.8.7 shows the relationship between addresses of the 4-M byte ROM and those of M16C.In this mode, memory isbanked every 512 K bytes,so that data access in differentbanks requires switchingover banks. However, dataon bank boundaries whenoffset bit = 0 can be accessedsuccessively by settingthe offset bit to 1, becausein which case thememory address is offset by4000016. For example, twobytes of data located at addresses0FFFFF16 and10000016 of 4-Mbyte ROMcan be accessed successivelywithout having tochange the bank bit by settingthe offset bit to 1 andthen accessing addresses07FFFF16 and 80000016.On the other hand, theSRAM’s chip select assumes_______that CS0=1 (not selected)_______and CS2=0 (selected), so_______connect CS0 with S2 and___________CS2 with S1. If the SRAMdoesn’t have a bipolar chipselect input terminal, decode_______ _______CS0 and CS2 externally.An example of connecting the MCU withexternal memories in expansion mode 2(M30622MC, Microprocessor mode)M30622MCD0 to D7A0 to A16A17A19CS1CS2CS3RDCS0WR817DQ0 to DQ7AD0 to AD16AD17AD18AD19AD20AD21OECSDQ0 to DQ7AD0 to AD16OES2S1Note: If only one chip select terminal (S1 or S2) is present,decoding by use of an external circuit is required.Figure 1.8.6. An example of connecting the MCU with externalmemories in expansion mode 2W4-M byte ROM128-K byte SRAM25