Protection - Renesas M16C Series User Manual

M30240 Group

1.2.11 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 1.14 shows the protect register. The values in the
processor mode register 0 (address 0004
control register 0 (address 0006
synthesizer registers 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 000A
0 and 1 write-enable bit (bit 1 at 000A
to an address. The program must therefore be written to return these bits to "0".
Protect register
b7 b6 b5 b4 b3
Figure 1.14: Protect register
Rev.1.00 Sep 24, 2003 Page 27 of 360
16
), system clock control register 1 (address 0007
16
) do not automatically return to "0" after a value has been written
16
b2 b1 b0
Symbol
O
PRCR
Bit symbol
Enables writing to system clock
control registers 0 and 1 (addresses
PRC0
0006
16
synthesizer registers (addresses
03DB
16
PRC1 Enables writing to processor mode
registers 0 and 1 (addresses 0004
and 0005
Reserved bit
Nothing is assigned.
These bits can neither be set nor reset. When read, their contents are
indeterminate.
), processor mode register 1 (address 0005
Address When reset
000A XXXXX000
16 2
Bit name
0 : Write-inhibited
1 : Write-enabled
) and frequency
and 0007
16
)
to 03DF
16
0 : Write-inhibited
1 : Write-enabled
16
)
16
Must always be set to "0"
), system clock
16
) and frequency
16
) and processor mode register
16
Function R W
Protection