CHAPTER 5 CLOCK GENERATION FUNCTION
User’s Manual U16896EJ2V0UD
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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.
(1/2)
FRC
Used
Not used
FRC
0
1
Use of subclock on-chip feedback resistor
PCC
MCK
MFRC
CLS
Note
CK3
CK2
CK1
CK0
Oscillation enabled
Oscillation stopped
MCK
0
1
Control of main clock oscillator
Used
Not used
MFRC
0
1
Use of main clock on-chip feedback resistor
After reset: 03H R/W Address: FFFFF828H
Main clock operation
Subclock operation
CLS
Note
0
1
Status of CPU clock (f
CPU
)
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.
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Note
The CLS bit is a read-only bit.