M30201F4-XXXSP View Datasheet(PDF) - MITSUBISHI ELECTRIC

Part Name

Description

MFG CO.

M30201F4-XXXSP

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

MITSUBISHI ELECTRIC  

PCrloctekcGtioennerating Circuit

Mitsubishi microcomputers

M30201 Group

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 1.21 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 P4 direction register

(address 03EA16) can only be changed when the respective bit in the protect register is set to “1”. There-

fore, important outputs can be allocated to port P4.

If, after “1” (write-enabled) has been written to the port P4 direction register write-enable bit (bit 2 at address

000A16), a value is written to any address, the bit automatically reverts to “0” (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 “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 XXXXX0002

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

PRC2

Enables writing to port P4 direction 0 : Write-inhibited

register (address 03EA16) (Note)

1 : Write-enabled

RW

Nothing is assigned.

These bits can neither be set nor reset. When read, their contents are

indeterminate.

Note: Writing a value to an address after “1” is written to this bit returns the bit

to “0” . Other bits do not automatically return to “0” and they must therefore

be reset by the program.

Figure 1.21. Protect register

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