M16CSLASH29 datasheet(93/499 Pages) RENESAS

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8. Protection

page 69

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 the PRC0 bit: CM0, CM1, CM2, PLC0, ROCR, PCLKR, and CCLKR

• Registers protected by the PRC1 bit: PM0, PM1, PM2, TB2SC, INVC0, and INVC1

• Registers protected by the PRC2 bit: PD9 , PACR, S4C, and NDDR

• Registers protected by the PRC3 bit: VCR2 and D4INT

The PRC2 bit is set to 0 (write enabled) when data is written to the SFR area after setting the PRC2 bit to 1

(write enable). Set registers PD9, PACR, S4C and NDDR 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. Bits PRC3, PRC1, and PRC0 are not set to 0 even if

data is written to the SFR area. Set bits PRC3, PRC1, and PRC0 to 0 by program.

Protect Register

Symbol

Address

After Reset

PRCR

000A16

XX0000002

Bit Name

Bit Symbol

b7 b6 b5 b4 b3 b2 b1 b0

PRC1

PRC0

PRC2

Function

Nothing is assigned. If necessary, set to 0.

When read, its content is undefined

Reserved bit

Set to 0

Protect bit 0

Protect bit 1

Protect bit 2

PRC3

Protect bit 3

Enable write to registers VCR2 and

D4INT

(b5-b4)

(b7-b6)

NOTE:

1. The PRC2 bit is set to 0 when writing into the SFR area after the PRC2 bit is set to 1. Bits

PRC0, PRC1, and PRC3 are not automatically set to 0. Set them to 0 by program.

Enable write to register CM0, CM1,

CM2, ROCR, PLC0, PCLKR, and

CCLKR

Enable write to registers PM0, PM1,

PM2, TB2SC, INVC0, and INVC1

0: Write protected

1: Write enabled

0: Write protected

1: Write enabled

Enable write to registers PD9,

PACR, S4C, and NDDR

0: Write protected

1: Write enabled(1)

0: Write protected

1: Write enabled

Figure 8.1 PRCR Register

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