upd70f3422gj-gae-qs-ax Renesas Electronics Corporation., upd70f3422gj-gae-qs-ax Datasheet - Page 140

• Manufacturer Part Number: upd70f3422gj-gae-qs-ax
• Description: 32-bit Single-chip Microcontroller
• Manufacturer: Renesas Electronics Corporation.

Chapter 4
140
Initial Value
Address
Caution
Access
(3)
PHCMD - Command protection register
The 8-bit PHCMD register is write-only. It is used to protect other registers from
unintended writing.
This register must be written in 8-bit units.
FFFF F800
The contents of this register is undefined.
PHCMD protects the registers that may have a significant influence on the
application system from inadvertent write access, so that the system does not
stop in case of a program hang-up.
Any data written to this register is ignored. Only the write action is monitored.
After writing to the PHCMD register, you are permitted to write once to one of
the protected registers. This must be done immediately after writing to the
PHCMD register. After the second write action, or if the second write action
does not follow immediately, all protected registers are write-locked again.
In case a high level programming language is used, make sure that the
compiler translates the two write instructions to PHCMD and the protected
register into two consecutive assembler “store” instructions.
With this method, the protected registers can only be rewritten in a specific
sequence. Illegal write access to a protected register is inhibited.
The following registers are protected by PHCMD:
An invalid write attempt to one of the above registers sets the error flag
PHS.PRERR. PHS.PRERR is also set, if a write access to PHCMD is not
immediately followed by an access to one of the protected registers.
Preliminary User’s Manual U17566EE1V2UM00
– CKC:
– FCC:
– ICC:
– PCC:
– SCC:
– TCC:
– WCC:
W
X
7
H
Clock control register
FOUTCLK control register
I
Processor clock control register
SPCLK control register
Watch Timer clock control register
Watchdog timer clock control register
2
.
W
6
X
C clock control register
W
X
5
W
X
4
W
X
3
W
X
2
Clock Generator
W
X
1
W
X
0