
CHAPTER 6 CLOCK GENERATOR
User’s Manual U17473EJ2V0UD
152
6.6.7 Condition before changing CPU clock and processing after changing CPU clock
Condition before changing the CPU clock and processing after changing the CPU clock are shown below.
Table 6-6. Changing CPU Clock
CPU Clock
Before Change
After Change
Condition Before Change
Processing After Change
X1 clock
Stabilization of X1 oscillation
MSTOP = 0, OSCSEL = 1, EXCLK = 0
After elapse of oscillation stabilization time
Internal high-speed oscillator can be
stopped (RSTOP = 1).
Clock supply to CPU is stopped for 4.06
to 16.12
μs after AMPH has been set to 1.
Internal high-
speed oscillation
clock
External main
system clock
Enabling input of external clock from EXCLK
pin
MSTOP = 0, OSCSEL = 1, EXCLK = 1
Internal high-speed oscillator can be
stopped (RSTOP = 1).
Clock supply to CPU is stopped for the
duration of 160 external clocks from the
EXCLK pin after AMPH has been set to 1.
X1 clock
X1 oscillation can be stopped (MSTOP = 1).
External main
system clock
Internal high-
speed oscillation
clock
Oscillation of internal high-speed oscillator
RSTOP = 0
External main system clock input can be
disabled (MSTOP = 1).
Internal high-
speed oscillation
clock
Operating current can be reduced by
stopping internal high-speed oscillator
(RSTOP = 1).
X1 clock
X1 oscillation can be stopped (MSTOP = 1).
External main
system clock
XT1 clock
Stabilization of XT1 oscillation
XTSTART = 0, EXCLKS = 0,
OSCSELS = 1, or XTSTART = 1
After elapse of oscillation stabilization time
External main system clock input can be
disabled (MSTOP = 1).
Internal high-
speed oscillation
clock
Operating current can be reduced by
stopping internal high-speed oscillator
(RSTOP = 1).
X1 clock
X1 oscillation can be stopped (MSTOP = 1).
External main
system clock
External
subsystem clock
Enabling input of external clock from
EXCLKS pin
XTSTART = 0, EXCLKS = 1,
OSCSELS = 1
External main system clock input can be
disabled (MSTOP = 1).
Internal high-
speed oscillation
clock
Oscillation of internal high-speed oscillator
and selection of internal high-speed
oscillation clock as main system clock
RSTOP = 0, MCS = 0
XT1 oscillation can be stopped or external
subsystem clock input can be disabled
(OSCSELS = 0).
X1 clock
Stabilization of X1 oscillation and selection
of high-speed system clock as main system
clock
MSTOP = 0, OSCSEL = 1, EXCLK = 0
After elapse of oscillation stabilization time
MCS = 1
XT1 oscillation can be stopped or external
subsystem clock input can be disabled
(OSCSELS = 0).
Clock supply to CPU is stopped for 4.06
to 16.12
μs after AMPH has been set to 1.
XT1 clock,
external
subsystem clock
External main
system clock
Enabling input of external clock from EXCLK
pin and selection of high-speed system
clock as main system clock
MSTOP = 0, OSCSEL = 1, EXCLK = 1
MCS = 1
XT1 oscillation can be stopped or external
subsystem clock input can be disabled
(OSCSELS = 0).
Clock supply to CPU is stopped for the
duration of 160 external clocks from the
EXCLK pin after AMPH has been set to 1.
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