Datasheet

CHAPTER 5 CLOCK GENERATOR
User’s Manual U18698EJ1V0UD
139
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 5-6. 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 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).
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
• OSCSELS = 1
• After elapse of oscillation stabilization time
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
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 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 (OSCSELS
= 0).