M16C User Manual.pdf

External BusesMitsubishi microcomputersM16C / 62 GroupSINGLE-CHIP 16-BIT CMOS MICROCOMPUTER5.3 Memory Space Expansion FeaturesHere follows the description of the memory space expansion function.(1) Normal Mode 1M byte memory space(2) Memory space expansion mode1 1.2M byte memory space(3) Memory space expansion mode2 4M byte memory spaceUse bits 5 and 4(PM15,PM14) of processor mode register 1 to select a desired mode.Figure 5.3.1 showsthe processor mode register 1.Processor mode register 1 (Note 1)b7 b6 b5 b4 b3 b2 b1 b000Symbol Address When resetPM1 000516 00000XX02Bit symbol Bit nameFunctionReserved bit Must always be set to “0”Nothing is assigned.In an attempt to write to these bits, write “0”. The value, if read, turnsout to be indeterminate.PM13PM14PM15Internal reserved areaexpansion bit (Note 2)Memory areaexpansion bit (Note 3)0: The same internal reservedarea as that of M16C/60 andM16C/61 group1: Expands the internal RAM areaand internal ROM area to 23 Kbytes and to 256K bytesrespectively. (Note 2)b5 b40 0 : Normal mode(Do not expand)0 1 : Inhibited1 0 : Memory area expansionmode 11 1 : Memory area expansionmode 2Reserved bit Must always be set to “0”PM17 Wait bit 0 : No wait state1 : Wait state insertedR WNote 1: Set bit 1 of the protect register (address 000A16) to “1” when writing new values to this register.Note 2: Be sure to set this bit to 0 except products whose RAM size and ROM size exceed 15K bytesand 192K bytes respectively.In using M30624MG/FG, a product having a RAM of more than 15K bytes and a ROM of morethan 192K bytes, set this bit to 1 at the beginning of user program.Specify D000016 or a subsequent address, which becomes an internal ROM area if PM13 is setto “0” at the time reset is revoked, for the reset vector table of user program.Note 3: With the processor running in memory expansion mode or in microprocessor mode, setting thisbit provides the means of expanding the external memory area. (Normal mode: up to 1M byte,expansion mode 1: up to 1.2 M bytes, expansion mode 2: up to 4M bytes)For details, see “Memory space expansion functions”.Figure 5.3.1. Processor mode register 1512