M16C/62 Group DATASHEET

Software ResetMitsubishi microcomputersM16C / 62 GroupSINGLE-CHIP 16-BIT CMOS MICROCOMPUTERSoftware ResetWriting “1” to bit 3 of the processor mode register 0 (address 000416) applies a (software) reset to themicrocomputer. A software reset has the same effect as a hardware reset. The contents of internal RAMare preserved.Processor Mode(1) Types of Processor ModeOne of three processor modes can be selected: single-chip mode, memory expansion mode, and microprocessormode. The functions of some pins, the memory map, and the access space differ according tothe selected processor mode.• Single-chip modeIn single-chip mode, only internal memory space (SFR, internal RAM, and internal ROM) can beaccessed. Ports P0 to P10 can be used as programmable I/O ports or as I/O ports for the internalperipheral functions.• Memory expansion modeIn memory expansion mode, external memory can be accessed in addition to the internal memoryspace (SFR, internal RAM, and internal ROM).In this mode, some of the pins function as the address bus, the data bus, and as control signals. Thenumber of pins assigned to these functions depends on the bus and register settings. (See “BusSettings” for details.)• Microprocessor modeIn microprocessor mode, the SFR, internal RAM, and external memory space can be accessed. Theinternal ROM area cannot be accessed.In this mode, some of the pins function as the address bus, the data bus, and as control signals. Thenumber of pins assigned to these functions depends on the bus and register settings. (See “BusSettings” for details.)(2) Setting Processor ModesThe processor mode is set using the CNVSS pin and the processor mode bits (bits 1 and 0 at address000416). Do not set the processor mode bits to “102”.Regardless of the level of the CNVSS pin, changing the processor mode bits selects the mode. Therefore,never change the processor mode bits when changing the contents of other bits. Also do not attempt toshift to or from the microprocessor mode within the program stored in the internal ROM area.• Applying VSS to CNVSS pinThe microcomputer begins operation in single-chip mode after being reset. Memory expansion modeis selected by writing “012” to the processor mode is selected bits.• Applying VCC to CNVSS pinThe microcomputer starts to operate in microprocessor mode after being reset.Figure 1.9.1 shows the processor mode register 0 and 1.Figure 1.10.1 shows the memory maps applicable for each of the modes when memory area dose not beexpanded (normal mode).27