M306H2MC-XXXFP Datasheet, PDF (41/210 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with DATA ACQUISITION CONTROLLER

MITSUBISHI MICROCOMPUTERS
M306H2MC-XXXFP
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
with DATA ACQUISITION CONTROLLER
2.6 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 2.6.1 shows the protect register. The values in the
processor mode register 0 (address 000416), processor mode register 1 (address 000516), system clock
control register 0 (address 000616), system clock control register 1 (address 000716), port P9 direction
register (address 03F316) , SI/O3 control register (address 036216) and SI/O4 control register (address
036616) 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.
If, after “1” (write-enabled) has been written to the port P9 direction register and SI/Oi control register
(i=3,4) write-enable bit (bit 2 at address 000A16), a value is written to any address, the bit automatically
reverts to “0” (write-inhibited). However, the system clock control registers 0 and 1 write-enable bit (bit 0
at 000A16) and processor mode register 0 and 1 write-enable bit (bit 1 at 000A16) do not automatically
return to “0” after a value has been written to an address. The program must therefore be written to return
these bits to “0”.
Protect register
b7 b6 b5 b4 b3 b2 b1 b0
Symbol
PRCR
Address When reset
000A16 XXXXX0002
Bit symbol
Bit name
Function
PRC0
Enables writing to system clock
control registers 0 and 1 (addresses ^{0 : Write-inhibited}
000616 and 000716)
1 : Write-enabled
PRC1
Enables writing to processor mode
registers 0 and 1 (addresses 000416
and 000516)
0 : Write-inhibited
1 : Write-enabled
PRC2
Enables writing to port P9 direction
register (address 03F316) and to
0 : Write-inhibited
SI/Oi control register (i=3,4)
1 : Write-enabled
(addresses 036216 and 036616)(Note)
RW
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 2.6.1 Protect register
Rev. 1.0
40