M16C6K9 Datasheet, PDF (39/292 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

M16C/6K9 Group
Protection
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) can only be changed when the respec-
tive bit in the protect register is set to “1”.
Protect register
b7 b6 b5 b4 b3 b2 b1 b0
0
Symbol
PRCR
Address When reset
000A16 XXXXX0002
Bit symbol
PRC0
Bit name
Function
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 ^{0 : Write-inhibited}
and 000516)
1 : Write-enabled
Reserved bit
Must be "0"
Nothing is assigned.
In an attempt to write to these bits, write “0”. The value, if read, turns out to be
indeterminate.
RW
Fig.WA-6 Protect register
Rev.1.00 Jun 06, 2003 page 39 of 290