M306H2MC datasheet(21/210 Pages) RENESAS

21 / 210 page

Rev. 1.0

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

with DATA ACQUISITION CONTROLLER

MITSUBISHI MICROCOMPUTERS

M306H2MC-XXXFP

2.4 Processor Mode

(1) Types of Processor Mode

Processor mode can be used at microprocessor mode.

One of three processor modes can be selected:single-chip mode,memory expansion mode,and mi-

cro-processor mode.The functions of some pins,the memory map,and the access space differ accord-

ing to the selected processor mode.

• Single-chip mode

In single-chip mode,only internal memory space (SFR,internal RAM,and internal ROM)can be

accessed.Ports P0 to P10 can be used as programmable I/O ports or as I/O ports for the internal

peripheral functions.

• Memory expansion mode

In memory expansion mode,external memory can be accessed in addition to the internal memory

space (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.The

number of pins assigned to these functions depends on the bus and register settings.(See "Bus

Settings " for details..)

• Microprocessor mode

In microprocessor mode,the SFR,internal RAM,and external memory space can be accessed.The

internal ROM area cannot be accessed.

In this mode,some of the pins function as the address bus,the data bus,and as control signals.The

number of pins assigned to these functions depends on the bus and register settings.(See "2.4.1 Bus

Settings " for details..)

(2) Setting Processor Modes

The processor mode is set using the CNVSS pin and the processor mode bits (bits 1 and 0 at address

000416).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 to

shift to or from the microprocessor mode within the program stored in the internal ROM area.

• Applying VSS to CNVSS pin

The microcomputer begins operation in single-chip mode after being reset.Memory expansion mode

is selected by writing "012 " to the processor mode is selected bits..

• Applying VCC to CNVSS pin

The microcomputer starts to operate in microprocessor mode after being reset.

Figure 2.4.1 shows the processor mode register 0 and 1.

Figure 2.4.2 shows the memory maps applicable for each of the modes when memory area dose not

be expanded (normal mode).

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