CHAPTER 5 CLOCK GENERATOR
103
User’s Manual U11302EJ4V0UM
Figure 5-3. Format of Processor Clock Control Register
Notes 1.
Bit 5 is a read-only bit.
2.
This bit can be set to 1 only when the subsystem clock is not used.
3.
When the CPU is operating on the subsystem clock, MCC should be used to stop the main system
clock oscillation. The STOP instruction should not be used.
Cautions 1. Bit 3 must be set to 0.
2. Do not set MCC while an external clock is being input. This is because the X2 pin is pulled
up to V
DD
.
Remarks 1.
f
X
:
Main system clock oscillation frequency
2.
f
XT
: Subsystem clock oscillation frequency
PCC0
PCC
<7>
<6>
<5>
<4>
3
2
Symbol
1
0
CSS
CPU clock (f
CPU
) selection
FFFBH
PCC1
0
PCC2
CSS
CLS
FRC
MCC
Address
After reset
R/W
04H
R/W
Note 1
f
X
f
X
/2
f
X
/2
2
f
X
/2
3
f
X
/2
4
f
XT
/2
Other than above
Setting prohibited
CLS
CPU clock status
0
Main system clock
1
Subsystem clock
FRC
Subsystem clock feedback resistor selection
0
Internal feedback resistor used
1
Internal feedback resistor not used
Note 2
MCC
Main system clock oscillation control
Note 3
0
Oscillation possible
1
Oscillation stopped
PCC2
0
0
0
0
1
0
0
1
0
1
PCC1
0
0
1
1
0
0
0
1
1
0
PCC0
0
1
0
1
0
0
1
0
1
0
0
0
R/W
R
R/W
R/W
Содержание mPD780204
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