M16C62_M Datasheet, PDF (322/615 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/60 SERIES

Protect
Mitsubishi microcomputers
M16C / 62A Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
(1) Clearing the protect (set to write-enabled state)
b7
b0 _{Protect register [Address 000A16]}
1 _PRCR
Enables writing to system clock control registers 0 and 1 (addresses 000616 and 000716)
1 : Write-enabled
Enables writing to port P9 direction register (address 03F316) and SI/Oi control register
(i=3,4) (addresses 036216 and 036616)
0 : Write-inhibited
1 : Write-enabled
(2)
Setting system clock control register i (i = 0, 1)
(3) Setting the protect (set to write-inhibited state)
b7
b0
Protect register [Address 000A16]
0 _PRCR
Enables writing to system clock control registers 0 and 1 (addresses 000616 and 000716)
0 : Write-inhibited
Enables writing to port P9 direction register (address 03F316) and SI/Oi control register
(i=3,4) (addresses 036216 and 036616)
0 : Write-inhibited
1 : Write-enabled
(4) Clearing the protect (set to write-enabled state)
b7
b0
Protect register [Address 000A16]
1
PRCR
Enables writing to system clock control registers 0 and 1 (addresses 000616 and 000716)
0 : Write-inhibited
1 : Write-enabled
Enables writing to port P9 direction register (address 03F316) and SI/Oi control register (
i=3,4) (addresses 036216 and 036616)
1 : Write-enabled
(5)
Changes in port P9 or changes in SI/Oi control register (i=3,4)
Figure 2.1.2. Set-up procedure for protect function
2.1.3 Precaution for Protect
(1) The write-enable bit of port 9 direction register and SI/Oi control register (i=3,4) goes to “0”
when the next write instruction is executed after write-enabled state is readied. Make
changes in input/output and SI/Oi control register (i=3,4) immediately after the instruction that
sets “1” in the write-enable bit of port P9 direction register and SI/Oi control register
(i=3,4)(avoid causing an interrupt). Also take measures to prevent DMA transfer from being
executed.
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