M16C28 Datasheet, PDF (86/423 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/Tiny SERIES

M16C/28 Group (M16C/28, M16C/28B)
8. Protection
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, LPCC1, PLC0, ROCR and PCLKR registers
• Registers protected by PRC1 bit: PM0, PM1, PM2, TB2SC, INVC0 and INVC1 registers
• Registers protected by PRC2 bit: PD9 , PACR, S4C and NDDR registers
• Registers protected by PRC3 bit: VCR2 and D4INT registers
The PRC2 bit is set to "0" (write enabled) if data is written to the SFR area after setting the PRC2 bit to "1"
(write enable). Set the PD9, PACR, S4C and NDDR registers immediately after setting the PRC2 bit in the
PRCR register to "1" (write enable). Do not generate an interrupt or a DMA transfer between the instruction
to set the PRC2 bit to "1" and the following instruction. The PRC0, PRC1 and PRC3 bits are not set to "0"
even if data is written to the SFR area. Set the PRC0, PRC1 and PRC3 bits to "0" by program.
Protect Register
b7 b6 b5 b4 b3 b2 b1 b0
00
Symbol
PRCR
Address
000A16
Bit Symbol
Bit Name
PRC0
Protect Bit 0
PRC1
Protect Bit 1
PRC2
Protect Bit 2
After Reset
XX00000 02
Function
RW
Enable write to CM0, CM1, CM2,
LPCC1, ROCR, 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, PACR
and S4C registers
RW
0 : Write protected
1 : Write enabled ⁽¹⁾
PRC3
Protect Bit 3
Enable write to VCR2 and D4INT
registers
RW
0 : Write protected
1 : Write enabled
(b5-b4)
Reserved Bit
Set to "0"
RW
(b7-b6)
Nothing is assigned. When write, set to "0". When read, its
content is indeterminate.
NOTE:
1. The PRC2 bit is set to "0" if data is written to the SFR area after the PRC2 bit is set to "1". The
PRC0, PRC1 and PRC3 bits are not automatically set to "0". Set them to "0" by program.
Figure 8.1 PRCR Register
Rev. 2.00 Jan. 31, 2007 ^{page 66} of 385
REJ09B0047-0200