M16C6K7 Datasheet, PDF(39/285 Page) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

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M16C6K7 Datasheet, PDF (39/285 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

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Rev.1.0

CPrloctekcGtioennerating Circuit

Mitsubishi microcomputers

M16C / 6K7 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. Fig.WA-6 shows the protect register. The values in the processor mode

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

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

03F316) , SI/O3 control register (address 036216) and SI/O4 control register (address 036616) can only be

changed when the respective bit in the protect register is set to â1â. Therefore, important outputs can be

allocated to port P9.

If, after â1â (write-enabled) has been written to the port P9 direction register and SI/Oi control register (i=3,4)

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

RW

PRC1

Enables writing to processor mode

registers 0 and 1 (addresses 000416

0 : Write-inhibited

and 000516)

1 : Write-enabled

PRC2

Enables writing to port P9 direction

register (address 03F316)

0 : Write-inhibited

and SI/Oi control register (i=3,4)

1 : Write-enabled

(address 036216 and 036616 ) (Note)

Nothing is assigned.

In an attempt to write to these bits, write â0â. 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

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

reset by the program.

Fig.WA-6 Protect register

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