M306V2ME Datasheet, PDF(46/276 Page) Mitsubishi Electric Semiconductor – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER and ON-SCREEN DISPLAY CONTROLLER　

English

English German Russian Spanish Italian Polish Chinese Japanese Korean French Portuguese	Language :

M306V2ME Datasheet, PDF (46/276 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER and ON-SCREEN DISPLAY CONTROLLER　

◁

MITSUBISHI MICROCOMPUTERS

M306V2ME-XXXFP

M306V2EEFP

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER

and ON-SCREEN DISPLAY CONTROLLER

2.6 Protection

The protection function is provided so that the values in important registers cannot be changed in the event

that the program runs out of control. Figure 2.6.1 shows the protect register. The values in the processor

mode register 0 (address 000416), processor mode register 1 (address 000516), system clock control reg-

ister 0 (address 000616), system clock control register 1 (address 000716) and port P9 direction register

(address 03F316) can only be changed when the respective bit in the protect register is set to â1â. There-

fore, important outputs can be allocated to port P9.

If, after â1â (write-enabled) has been written to the port P9 direction register write-enable bit (bit 2 at address

000A16), a value is written to any address, the bit automatically reverts to â0â (write-inhibited). However, the

system clock control registers 0 and 1 write-enable bit (bit 0 at 000A16) and processor mode register 0 and

1 write-enable bit (bit 1 at 000A16) do not automatically return to â0â after a value has been written to an

address. The program must therefore be written to return these bits to â0â.

Protect register

b7 b6 b5 b4 b3 b2 b1 b0

Symbol

PRCR

Address When reset

000A16 XXXXX0002

Bit symbol

PRC0

Bit name

Enables writing to system clock

control registers 0 and 1 (addresses

000616 and 000716)

Function

0 : Write-inhibited

1 : Write-enabled

PRC1

Enables writing to processor mode

registers 0 and 1 (addresses 0004 16

and 000516)

0 : Write-inhibited

1 : Write-enabled

PRC2

Enables writing to port P9 direction

register (address 03F3 16)

(Note)

0 : Write-inhibited

1 : Write-enabled

RW

Nothing is assigned.

In an attempt to write to these bits, write â0.â The value, if read, turns out to be

indeterminate.

Note: Writing a value to an address after â1â is written to this bit returns the bit

to â0.â Other bits do not automatically return to â0â and they must therefore

be reset by the program.

Figure 2.6.1 Protect register

Rev. 1.0

46

▷