Protection - Renesas M16C/29 Series Hardware Manual

M16C/29 Group

8. Protection

In the event that a program runs out of control, this function protects the important registers so that they will
not be rewritten easily. Figure 8.1 shows the PRCR register. The following lists the registers protected by
the PRCR register.
• Registers protected by PRC0 bit: CM0, CM1, CM2, PLC0, ROCR, PCLKR, and CCLKR registers
• Registers protected by PRC1 bit: PM0, PM1, PM2, TB2SC, INVC0 and INVC1 registers
• Registers protected by PRC2 bit: PD9 , PACR and S4C registers
• Registers protected by PRC3 bit: VCR2 and D4INT registers
Set the PRC2 bit to "1" (write enabled) and then write to any address, and the PRC2 bit will be cleared to "0"
(write protected). The registers protected by the PRC2 bit should be changed in the next instruction after
setting the PRC2 bit to "1". Make sure no interrupts or DMA transfers will occur between the instruction in
which the PRC2 bit is set to "1" and the next instruction. The PRC0, PRC1 and PRC3 bits are not automati-
cally cleared to "0" by writing to any address. They can only be cleared in a program.
Protect register
b7 b6 b5 b4 b3 b2
0 0
Note: The PRC2 bit is set to 0 by writing to any address after setting it to 1 . Other bits are not set to 0
by writing to any address, and must therefore be set in a program.
Figure 8.1. PRCR Register
Rev.1.00 Nov 01,2004
REJ09B0101-0100Z
b1 b0
Symbol
PRCR
Bit symbol
PRC0 Protect bit 0
PRC1
Protect bit 1
PRC2
Protect bit 2
PRC3 Protect bit 3
Reserved bit
(b5-b4)
Nothing is assigned. When write, set to 0 . When read, its
content is indeterminate.
(b7-b6)
page 60 of 402
Address After reset
000A XX000000
16 2
Bit name
Enable write to CM0, CM1, CM2,
ROCR, PLC0, PCLKR, and CCLKR
registers
0 : Write protected
1 : Write enabled
Enable write to PM0, PM1, PM2,
TB2SC, INVC0 and INVC1
registers
0 : Write protected
1 : Write enabled
Enable write to PD9, PACR
and S4C registers
0 : Write protected
1 : Write enabled
Enable write to VCR2 and D4INT
registers
0 : Write protected
1 : Write enabled
Must set to 0
8. Protection
Function
RW
RW
RW
RW
RW
RW