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Chapter 4
Clock Generator
Preliminary User’s Manual U17566EE1V2UM00
(3)
PRCMD - PSC write protection register
The 8-bit PRCMD register protects the register PSC from inadvertent write
access, so that the system does not stop in case of a program hang-up.
After data has been written to the PRCMD register, the first write access to
register PSC is valid. All subsequent write accesses are ignored. Thus, the
value of PSC can only be rewritten in a specified sequence, and illegal write
access is inhibited.
Access
This register can only be written in 8-bit units.
Address
FFFF F1FC
H
Initial Value
The contents of this register is undefined.
Caution
Before writing to PRCMD, make sure that all DMA channels are disabled.
Otherwise, a direct memory access could occur between the write access to
PRCMD and the write access to PSC. If that happens, the power save mode
may not be entered.
Caution
In case a high level programming language is used, make sure that the
compiler translates the two write instructions to PRCMD and PSC into two
consecutive assembler “store” instructions.
7
6
5
4
3
2
1
0
X
X
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X
X
X
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X
W
W
W
W
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W
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