M306H7MG-XXXFP Datasheet, PDF (42/329 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with DATA ACQUISITION CONTROLLER

M306H7MG-XXXFP/MC-XXXFP/FGFP
5. PROTECTION
5. 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 5.1 shows the PRCR register. The following lists the registers protected by the PRCR register.
• Registers protected by PRC0 bit: CM0, CM1 and PCLKR registers
• Registers protected by PRC1 bit: PM0, PM1 and 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
After reset
XX0000002
Bit symbol
PRC0
Bit name
Protect bit 0
PRC1
Protect bit 1
Function
RW
Enable write to CM0, CM1 and
PCLKR registers
RW
0 : Write protected
1 : Write enabled
Enable write to PM0, PM1 and
PM2 registers
0 : Write protected
RW
1 : Write enabled
PRC2
Protect bit 2
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 5.1 PRCR Register
Rev.2.10 Oct 25, 2006 Page 42 of 326
REJ03B0152-0210