Datasheet

M16C/6S Group Protection
R01DS0201EJ0502 Rev.5.02 page 46 of 203
Dec 25, 2012
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.
Figure 1.8.1. PRCR Register
Protect register
Symbol Address After reset
PRCR 000A
16 XX000000 2
Bit nameBit symbol
b7 b6 b5 b4 b3 b2 b1 b0
0 : Write protected
1 : Write enabled
PRC1
PRC0
PRC2
Function
RW
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.
0
0
RW
RW
RW
Nothing is assigned. When write, set to “0”. When read, its
content is interdeterminate.
Reserved bit
Must set to “0”
RW
Protect bit 0
Protect bit 1
Protect bit 2
Enable write to CM0, CM1, CM2,
PLC0 and PCLKR 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, S3C and
S4C registers
(b5-b3)
(b7-b6)
0