M16C6N4 Datasheet, PDF (92/406 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/60 SERIES

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M16C/6N Group (M16C/6N4)
9. Protection
9. 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 9.1 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 and S3C registers.
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.
Protect Register
b7 b6 b5 b4 b3 b2 b1 b0
000
Symbol
PRCR
Address
000Ah
After Reset
XX000000b
Bit Symbol
Bit Name
PRC0 Protect Bit 0
PRC1 Protect Bit 1
PRC2 Protect Bit 2
Function
RW
Enable write to CM0, CM1, CM2,
PLC0, PCLKR, CCLKR
registers
RW
0 : Write protected
1 : Write enabled
Enable write to PM0, PM1, PM2,
TB2SC, INVC0, INVC1
registers
RW
0 : Write protected
1 : Write enabled
Enable write to PD7, PD9, S3C
registers
0 : Write protected
RW
1 : Write enabled ⁽¹⁾
-
(b5-b3)
Reserved Bit
Set to "0"
RW
-
(b7-b6)
Nothing is assigned. When write, set to "0".
When read, their contents are indeterminate.
-
NOTE:
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.
Figure 9.1 PRCR Register
Rev.2.30 Oct 24, 2005 page 74 of 376
REJ09B0009-0230