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M30220MX-XXXGP

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

MITSUBISHI ELECTRIC  

Tentative Specifications REV.E

Mitsubishi microcomputers

Specifications in this manual are tentative and subject to change.

M30220 Group

Protection

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

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 1.9.8 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) can only be changed when the

respective bit in the protect register is set to “1”.

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 “0” after a value has been written to an

address. The program must therefore be written to return these bits to “0”.

Protect register

b7 b6 b5 b4 b3 b2 b1 b0

Symbol

PRCR

Address When reset

000A16 XXXXXX002

Bit symbol

Bit name

Function

PRC0

Enables writing to system clock

control registers 0 and 1 (addresses 0 : Write-inhibited

000616 and 000716)

1 : Write-enabled

PRC1

Enables writing to processor mode

registers 0 and 1 (addresses 000416

and 000516)

0 : Write-inhibited

1 : Write-enabled

Nothing is assigned.

In an attempt to write to these bits, write “0”. The value, if read, turns out to be

indeterminate.

RW

Figure 1.9.8. Protect register

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