M306V2EEFS datasheet(23/271 Pages) RENESAS

23 / 271 page

Rev.1.40

Oct 06, 2004 page 23 of 269

M306V2ME-XXXFP, M306V2EEFP

2.4 Processor Mode

2.4.1 Types of Processor Mode

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

processor mode. The functions of some pins, the memory map, and the access space differ according to

the selected processor mode.

(1) Single-chip mode

In single-chip mode, only internal memory space (SFR, OSD RAM, 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.

(2) Memory expansion mode

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

space (SFR, OSD RAM, 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 “2.4.3 Bus

Settings” for details.)

(3) Microprocessor mode

In microprocessor mode, the SFR, OSD RAM, 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 “2.4.3 Bus

Settings” for details.)

2.4.2 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.

(1) 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.

(2) Applying VCC to CNVSS pin

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

Figures 2.4.1 and 2.4.2 show the processor mode register 0 and 1.

Figure 2.4.3 shows the memory maps applicable for each of the modes.

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