CHAPTER 6 CLOCK GENERATOR
Preliminary User’s Manual U17260EJ3V1UD
166
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 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 5
µ
s
(MIN.) 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 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 5
µ
s
(MIN.) after AMPH has been set to 1.