UPD78F0838 Renesas Electronics Corporation., UPD78F0838 Datasheet - Page 212

• Manufacturer Part Number: UPD78F0838
• Description: 8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

5.6.7 Condition before changing CPU clock and processing after changing CPU clock
210
Internal high-
speed oscillation
clock
X1 clock
External main
system clock
Internal high-
speed oscillation
clock
X1 clock
External main
system clock
Internal high-
speed oscillation
clock
X1 clock
External main
system clock
XT1 clock,
external
subsystem clock
Before Change
Condition before changing the CPU clock and processing after changing the CPU clock are shown below.
CPU Clock
X1 clock
External main
system clock
Internal high-
speed oscillation
clock
XT1 clock
External
subsystem clock
Internal high-
speed oscillation
clock
X1 clock
External main
system clock
After Change
Stabilization of X1 oscillation
Enabling input of external clock from
EXCLK pin
Oscillation of internal high-speed oscillator
Stabilization of XT1 oscillation
Enabling input of external clock from
EXCLKS pin
Oscillation of internal high-speed oscillator
and selection of internal high-speed
oscillation clock as main system clock
Stabilization of X1 oscillation and selection
of high-speed system clock as 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 = 0
After elapse of oscillation stabilization time
MSTOP = 0, OSCSEL = 1, EXCLK = 1
RSTOP = 0
EXCLKS = 0, OSCSELS = 1
After elapse of oscillation stabilization time
EXCLKS = 1, OSCSELS = 1
RSTOP = 0, MCS = 0
MSTOP = 0, OSCSEL = 1, EXCLK = 0
After elapse of oscillation stabilization time
MCS = 1
MSTOP = 0, OSCSEL = 1, EXCLK = 1
MCS = 1
Preliminary User’s Manual U19748EJ1V0UD
CHAPTER 5 CLOCK GENERATOR
Table 5-5. Changing CPU Clock
Condition Before Change
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).
Internal high-speed oscillator can be
stopped (RSTOP = 1).
Clock supply to CPU is stopped for 4.06
to 16.12 s after AMPH has been set to
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.
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 s after AMPH has been set to
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.
Processing After Change