Renesas M16C FAMILY, User Manual

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Rev.2.00 Oct 16, 2006 page 4 of 354
REJ09B0340-0200
M30245 Group 2. Protect
2.1.1 Overview
'Protect' is a function that causes a value held in a register to be unchanged even when a program runs
away. The following is an overview of the protect function:
(1) Registers affected by the protect function
The registers affected by the protect function are:
(a) System clock control registers 0, 1 (addresses 0006
16
and 0007
16
)
(b) Processor mode registers 0, 1 (addresses 0004
16
and 0005
16
)
(c) Frequency synthesizer-related registers (address 03DB
16
to 03DF
16
)
The values in registers (a) through (c) cannot be changed in write-protect state. To change values in
the registers, put the individual registers in write-enabled state.
(2) Protect register
Figure 2.1.1 shows protect register.
2.1 Protect
Figure 2.1.1. Protect register
Protect register
Symbol Address When reset
PRCR 000A
16
XXXXX000
2
Bit name Bit symbol
b7 b6 b5 b4 b3 b2 b1 b0
0 : Write-inhibited
1 : Write-enabled
PRC1
PRC0
Function W R
Nothing is assigned.
When write, set “0”. When read, their contents are indeterminate.
0
Enables writing to system clock
control registers 0 and 1 (addresses
0006
16
and 0007
16
) and frequency
synthesizer registers (addresses
03DB
16
to 03DF
16
)
Enables writing to processor mode
registers 0 and 1 (addresses 0004
16
and 0005
16
)
Reserved Must always be set to “0”
0 : Write-inhibited
1 : Write-enabled