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RL78/G1A CHAPTER 5 CLOCK GENERATOR
R01UH0305EJ0200 Rev.2.00 174
Jul 04, 2013
5.6.5 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 5-4. Changing CPU Clock (1/2)
CPU Clock
Before Change After Change
Condition Before Change Processing After Change
X1 clock
Stabilization of X1 oscillation
• OSCSEL = 1, EXCLK = 0, MSTOP = 0
• After elapse of oscillation stabilization time
External main
system clock
Enabling input of external clock from the
EXCLK pin
• OSCSEL = 1, EXCLK = 1, MSTOP = 0
XT1 clock
Stabilization of XT1 oscillation
• OSCSELS = 1, EXCLKS = 0, XTSTOP = 0
• After elapse of oscillation stabilization time
High-speed on-
chip oscillator
clock
External
subsystem clock
Enabling input of external clock from the
EXCLKS pin
• OSCSELS = 1, EXCLKS = 1, XTSTOP = 0
Operating current can be reduced by
stopping high-speed on-chip oscillator
(HIOSTOP = 1).
High-speed on-
chip oscillator
clock
Enabling oscillation of high-speed on-chip
oscillator
• HIOSTOP = 0
• After elapse of oscillation accuracy
stabilization time
X1 oscillation can be stopped (MSTOP = 1).
External main
system clock
Transition not possible
−
XT1 clock
Stabilization of XT1 oscillation
• OSCSELS = 1, EXCLKS = 0, XTSTOP = 0
• After elapse of oscillation stabilization time
X1 oscillation can be stopped (MSTOP = 1).
X1 clock
External
subsystem clock
Enabling input of external clock from the
EXCLKS pin
• OSCSELS = 1, EXCLKS = 1, XTSTOP = 0
X1 oscillation can be stopped (MSTOP = 1).
High-speed on-
chip oscillator
clock
Enabling oscillation of high-speed on-chip
oscillator
• HIOSTOP = 0
• After elapse of oscillation accuracy
stabilization time
External main system clock input can be
disabled (MSTOP = 1).
X1 clock
Transition not possible
−
XT1 clock
Stabilization of XT1 oscillation
• OSCSELS = 1, EXCLKS = 0, XTSTOP = 0
• After elapse of oscillation stabilization time
External main system clock input can be
disabled (MSTOP = 1).
External main
system clock
External
subsystem clock
Enabling input of external clock from the
EXCLKS pin
• OSCSELS = 1, EXCLKS = 1, XTSTOP = 0
External main system clock input can be
disabled (MSTOP = 1).
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