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5.3 Registers
(1) Processor clock control register (PCC)
The PCC register is a special register. Data can be written to this register only in combination of specific
sequences (refer to 3.4.7 Special registers).
This register can be read or written in 8-bit or 1-bit units.
Reset sets this register to 03H.
After reset: 03H
PCC
FRC
FRC
MCK
•
Even if the MCK bit is set to 1 while the system is operating with the main clock as
the CPU clock, the operation of the main clock does not stop. It stops after the
CPU clock has been changed to the subclock.
•
When the main clock is stopped and the device is operating on the subclock, clear
the MCK bit to 0 and wait until the oscillation stabilization time has been secured by
the program before switching back to the main clock.
MFRC
CLS
Note The CLS bit is a read-only bit.
128
CHAPTER 5 CLOCK GENERATION FUNCTION
R/W
Address: FFFFF828H
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MCK
MFRC
CLS
Use of subclock on-chip feedback resistor
0
Used
1
Not used
Control of main clock oscillator
0
Oscillation enabled
1
Oscillation stopped
Use of main clock on-chip feedback resistor
0
Used
1
Not used
Note
0
Main clock operation
1
Subclock operation
User's Manual U16896EJ2V0UD
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Note
CK3
CK2
Status of CPU clock (f
)
CPU
CK1
CK0
(1/2)
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