Datasheet

78K0/Kx2-L CHAPTER 5 CLOCK GENERATOR
R01UH0028EJ0400 Rev.4.00 236
Sep 27, 2010
5.6.7 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 5-7. 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).
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).
X1 clock X1 oscillation can be stopped (MSTOP = 1).
KY2-L,
KA2-L,
KB2-L,
KC2-L
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).
KC2-L
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).
Remark Only 78K0/KC2-L is provided with a subsystem clock.