M16C6S_09 Datasheet, PDF (46/208 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

M16C/6S Group
Protection
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 1.8.1 shows the PRCR register. The following lists the registers protected by
the PRCR register.
• Registers protected by PRC0 bit: CM0, CM1, CM2, and PCLKR registers
• Registers protected by PRC1 bit: PM0, PM1, PM2 registers
• Registers protected by PRC2 bit: PD9, S3C and S4C 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 and PRC1 bits are not automatically
cleared to “0” by writing to any address. They can only be cleared in a program.
Protect register
b7 b6 b5 b4 b3 b2 b1 b0
0 00
Symbol
PRCR
Address
000A16
Bit symbol
Bit name
PRC0
Protect bit 0
PRC1
Protect bit 1
PRC2
Protect bit 2
After reset
XX0000002
Function
RW
Enable write to CM0, CM1, CM2,
PLC0 and PCLKR registers
RW
0 : Write protected
1 : Write enabled
Enable write to PM0, PM1, PM2,
TB2SC, INVC0 and INVC1
registers
RW
0 : Write protected
1 : Write enabled
Enable write to PD9, S3C and
S4C registers
RW
0 : Write protected
1 : Write enabled
(b5-b3)
Reserved bit
Must set to “0”
RW
(b7-b6)
Nothing is assigned. When write, set to “0”. When read, its
content is interdeterminate.
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 1.8.1. PRCR Register
Rev.5.01 Dec 10, 2009 page 46 of 201
REJ03B0014-0501