CHAPTER 5 CLOCK GENERATOR
Preliminary User’s Manual U16315EJ1V0UD
106
Figure 5-3. Format of Processor Clock Control Register (PCC)
Address: FFFBH After reset: 00H R/W
Note 1
Symbol
7
6
5
4
3
2
1
0
PCC
MCC
FRC
CLS
CSS
0
PCC2
PCC1
PCC0
MCC
Control of X1 oscillator operation
Note 2
0
Oscillation possible
1
Oscillation stopped
FRC
Subsystem clock feedback resistor selection
Note 3
0
On-chip feedback resistor used
1
On-chip feedback resistor not used
CLS
CPU clock status
0
X1 input clock or Ring-OSC clock
1
Subsystem clock
CPU Clock (f
CPU
) Selection
CSS
Note 4
PCC2
PCC1
PCC0
MCM0 = 0
MCM0 = 1
0
0
0
f
X
f
R
f
XP
0
0
1
f
X
/2
f
R
/2
f
XP
/2
0
1
0
f
X
/2
2
f
R
/2
2
f
XP
/2
2
0
1
1
f
X
/2
3
f
R
/2
3
f
XP
/2
3
0
1
0
0
f
X
/2
4
f
R
/2
4
f
XP
/2
4
0
0
0
0
0
1
0
1
0
0
1
1
1
1
0
0
f
XT
/2
Other than above
Setting prohibited
Notes 1.
Bit 5 is read-only.
2.
When the CPU is operating on the subsystem clock, MCC should be used to stop the X1 oscillator
operation. When the CPU is operating on the Ring-OSC clock, use bit 7 (MSTOP) of the main OSC
control register (MOC) to stop the X1 oscillator operation (this cannot be set by MCC). A STOP
instruction should not be used.
3.
The feedback resistor is required to adjust the bias point of the oscillation waveform to close to the
middle of the power supply voltage. Setting FRC to 1 can further reduce the current consumption in
the STOP mode, but only when the subsystem clock is not used.
4.
Be sure to switch CSS from 1 to 0 when bits 1 (MCS) and 0 (MCM0) of the main clock mode register
(MCM) are 1.
Caution
Be sure to set bit 3 to 0.
Remarks 1.
MCM0: Bit 0 of the main clock mode register (MCM)
2.
f
X
:
Main system clock oscillation frequency (X1 input clock oscillation frequency or Ring-OSC clock
oscillation frequency)
3.
f
R
:
Ring-OSC clock oscillation frequency
4.
f
XP
: X1 input clock oscillation frequency
5.
f
XT
: Subsystem clock oscillation frequency