M16CSLASH26 datasheet(49/239 Pages) RENESAS

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Protection

M16C/26 Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Renesas Technology Corp.

Under

development

Preliminary Specifications Rev. 0.9

Specifications in this manual are tentative and subject to change.

Protection

The protection function is provided so that the values in important registers cannot be changed in the event

that the program runs out of control. Figure 1.8.9 shows the protect register. The values in the processor

mode register 0 (address 000416), processor mode register 1 (address 000516), system clock control reg-

ister 0 (address 000616), system clock control register 1 (address 000716), oscillation stop detection regis-

ter (address 000C16), processor mode register 2 (001E16), peripheral clock select register (address

025E16), timer B2 special mode register (039E16), port P9 direction register (address 03F316), three-phase

PWM control register 0 (address 034816) and three-phase PWM control register 1 (address 034916) can

only be changed when the respective bit in the protect register is set to “1”. Therefore, important outputs

can be allocated to port P9.

Protect register

Symbol

Address

When reset

PRCR

000A16

XXX000002

Bit name

Bit symbol

0 : Write-inhibited

1 : Write-enabled

PRC1

PRC0

PRC2

Enables writing to processor mode

registers 0,1 and 2 (addresses 000

416,000516 and 001E16), timer B2

special mode register (address

039E16), three-phase PWM control

registers 0 and 1 (addresses

034816 and 034916)

Function

0 : Write-inhibited

1 : Write-enabled

Enables writing to system clock

control registers 0 and 1 (addresses

000616 and 000716

), oscillation stop

detection register (address 000C16),

peripheral clock select register

(address 025E16)

Enables writing to port P9 direction

0 : Write-inhibited

1 : Write-enabled

Nothing is assigned.

In an attempt to write to these bits, write 0 . The value, if read, turns out to be

indeterminate.

Note: Writing a value to an address after 1 is written to this bit returns the bit

to 0 . Other bits do not automatically return to 0 and they must therefore

be reset by the program.

Reserved bit

Must always set to "0"

PRC3

Enables writing to VCR2 (address

001A16) and D4INT (address 001F16)

0 : Write-inhibited

1 : Write-enabled

Figure 1.8.9. Protect register

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