M16C26 Datasheet, PDF (49/239 Pages) Renesas Technology Corp – 16-BIT CMOS SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/20 SERIES

Udenvdeelropment
Protection
Preliminary Specifications Rev. 0.9
Specifications in this manual are tentative and subject to change. _{M16C/26 Group}
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
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
b7 b6 b5 b4 b3 b2 b1 b0
0
Symbol
PRCR
Bit symbol
Address
000A16
When reset
XXX000002
Bit name
Function
RW
PRC0
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)
0 : Write-inhibited
1 : Write-enabled
PRC1
PRC2
PRC3
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)
Enables writing to port P9 direction
register (address 03F316) (note)
0 : Write-inhibited
1 : Write-enabled
0 : Write-inhibited
1 : Write-enabled
Enables writing to VCR2 (address _{0 : Write-inhibited}
001A16) and D4INT (address 001F16) _{1 : Write-enabled}
Reserved bit
Must always set to "0"
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.
Figure 1.8.9. Protect register
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