
Page 81
8
4
f
o
6
0
2
,
1
3
.
n
a
J
1
3
.
1
.
v
e
R
1
3
1
0
-
4
3
0
B
9
0
J
E
R
8. Clock Generation Circuit
)
T
3
8
/
C
2
3
M
,
3
8
/
C
2
3
M
(
p
u
o
r
G
3
8
/
C
2
3
M
8.5.1 Normal Operation Mode
The normal operation mode is further separated into six modes.
In normal operation mode, the CPU clock and peripheral function clock are supplied to operate the CPU
and peripheral function. The power consumption control is enabled by controlling the CPU clock fre-
quency. The higher the CPU clock frequency, the more processing power increases. The lower the CPU
clock frequency, the more power consumption decreases. When unnecessary oscillation circuits stop,
power consumption is further reduced.
8.5.1.1 High-Speed Mode
The main clock(1) becomes the CPU clock and the clock source for the peripheral function clock.
When the sub clock runs, fC32 can be used as a count source for the timers A and B.
8.5.1.2 Medium-Speed Mode
The main clock divided-by-2, -3, -4, -6, -8, -10, -12, -14, or -16 becomes the CPU clock. The main
clock is the clock source for the peripheral function clock. When the sub clock runs, fC32 can be used
as the count source for the timers A and B.
8.5.1.3 Low-Speed Mode
The sub clock becomes the CPU clock. The main clock is the count source for the peripheral function
clock. fC32 can be used as the count source for the timers A and B.
8.5.1.4 Low-Power Consumption Mode
The microcomputer enters low-power consumption mode when the main clock stops in low-speed
mode. The sub clock becomes the CPU clock. fC32 can be used as the count source for timers A and
B. Only fC32 can be used as the peripheral function clock. In low-power consumption mode, the MCD
register is set to "0816" (divide-by-8 mode). Therefore, when the main clock resumes running, the
microcomputer is in middle-speed mode (divide-by-8 mode).
8.5.1.5 On-chip Oscillator Mode
The on-chip oscillator clock divided-by-1(no division), -2, -3, -4, -6, -8, -10, -12, -14, or -16 becomes
the CPU clock. The on-chip oscillator clock is the clock source for the peripheral function clock. When
the sub clock runs, fC32 can be used as the count source for the timers A and B.
8.5.1.6 On-chip Oscillator Low-Power Consumption Mode
The microcomputer enters on-chip oscillator low-power consumption mode when the main clock stops
in on-chip oscillator mode. The on-chip oscillator clock divided-by-1(no division), -2, -3, -4, -6, -8, -10, -
12, -14, or -16 becomes the CPU clock. The on-chip oscillator clock is the clock source for the peripheral
function clock. When the sub clock runs, fC32 can be used as the count source for the timers A and B.
Switch the CPU clock after the clock to be switched to stabilizes. Sub clock oscillation will take longer(2)
to stabilize. Wait, by program, until the clock stabilizes directly after running the microcomputer on or
exiting stop mode.
To switch the on-chip oscillator to the main clock, enter medium-speed mode (divide-by-8) after the main
clock is divided by eight in on-chip oscillator mode (MCD register=0816).
Do not enter on-chip oscillator mode or on-chip oscillator low-power consumption mode from low-speed
mode or low-power consumption mode and vice versa.
NOTES:
1. When the CM17 bit is set to "1" (PLL clock as CPU clock source), the PLL clock is the main clock .
2. Contact your oscillator manufacturer for oscillation stabilization time.