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Rev.1.02 Jul 01, 2005 page 55 of 314
REJ09B0126-0102
M16C/6N Group (M16C/6NL, M16C/6NN) 8. Protection
Under development
This document is under development and its contents are subject to change.
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.
• The PRC0 bit protects the CM0, CM1, CM2, PLC0, PCLKR and CCLKR registers;
• The PRC1 bit protects the PM0, PM1, PM2, TB2SC, INVC0 and INVC1 registers;
• The PRC2 bit protects the PD7, PD9, S3C, S4C, S5C and S6C registers
(1)
.
NOTE:
1. The S5C and S6C registers are only in the 128-pin version.
Set the PRC2 bit to “1” (write enabled) and then write to any address, and the PRC2 bit will be set 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 set to “0” by
writing to any address. They can only be set to “0” in a program.
Figure 8.1 PRCR Register
RW
RW
RW
RW
PRC1
PRC0
PRC2
Protect Bit 1
Protect Bit 0
Protect Bit 2
Enable write to CM0, CM1, CM2,
PLC0, PCLKR, CCLKR
registers
0 : Write protected
1 : Write enabled
Enable write to PM0, PM1, PM2,
TB2SC, INVC0, INVC1
registers
0 : Write protected
1 : Write enabled
Enable write to PD7, PD9, S3C,
S4C, S5C, S6C registers
(2)
0 : Write protected
1 : Write enabled
(1)
Reserved Bit Set to "0"
RW
-
-
(b5-b3)
-
(b7-b6)
Nothing is assigned. When write, set to "0".
When read, their contents are indeterminate.
b7 b6 b5 b4 b3 b2 b1 b0
Protect Register
Symbol Address After Reset
PRCR 000Ah XX000000b
Bit NameBit Symbol Function
NOTES:
1. 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.
2. The S5C and S6C registers are only in the 128-pin version.
0 0
0