Condition Before Changing Cpu Clock And Processing After Changing Cpu Clock - NEC 78K0 Series User Manual

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.
CPU Clock
Before Change After Change
Internal high- X1 clock
speed oscillation
clock
External main
system clock
X1 clock Internal high-
speed oscillation
External main
clock
system clock
Internal high-
XT1 clock
speed oscillation
clock
X1 clock
External main
system clock
Internal high- External
speed oscillation subsystem clock
clock
X1 clock
External main
system clock
XT1 clock, Internal high-
external speed oscillation
subsystem clock clock
X1 clock
External main
system clock
166
CHAPTER 6 CLOCK GENERATOR
Table 6-6. Changing CPU Clock
Condition Before Change
Stabilization of X1 oscillation
• MSTOP = 0, OSCSEL = 1, EXCLK = 0
• After elapse of oscillation stabilization time
Enabling input of external clock from EXCLK
pin
• MSTOP = 0, OSCSEL = 1, EXCLK = 1
Oscillation of internal high-speed oscillator
• RSTOP = 0
Stabilization of XT1 oscillation
• XTSTART = 0, EXCLKS = 0,
OSCSELS = 1, or XTSTART = 1
• After elapse of oscillation stabilization time
Enabling input of external clock from
EXCLKS pin
• XTSTART = 0, EXCLKS = 1,
OSCSELS = 1
Oscillation of internal high-speed oscillator
and selection of internal high-speed
oscillation clock as main system clock
• RSTOP = 0, MCS = 0
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
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
Preliminary User's Manual U17260EJ3V1UD
Processing After Change
• Internal high-speed oscillator can be
stopped (RSTOP = 1).
• Clock supply to CPU is stopped for 5
(MIN.) after AMPH has been set to 1.
X1 oscillation can be stopped (MSTOP = 1).
External main system clock input can be
disabled (MSTOP = 1).
Operating current can be reduced by
stopping internal high-speed oscillator
(RSTOP = 1).
X1 oscillation can be stopped (MSTOP = 1).
External main system clock input can be
disabled (MSTOP = 1).
Operating current can be reduced by
stopping internal high-speed oscillator
(RSTOP = 1).
X1 oscillation can be stopped (MSTOP = 1).
External main system clock input can be
disabled (MSTOP = 1).
XT1 oscillation can be stopped or external
subsystem clock input can be disabled
(OSCSELS = 0).
• XT1 oscillation can be stopped or external
subsystem clock input can be disabled
(OSCSELS = 0).
• Clock supply to CPU is stopped for 5
(MIN.) after AMPH has been set to 1.
µ
s
µ
s