CHAPTER 6 CLOCK GENERATOR
Page 135 of 920
6.6.5
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 6 - 8 Changing CPU Clock (1/2)
CPU Clock
Condition Before Change
Processing After Change
Before Change
After Change
High-speed on-chip
oscillator clock
X1 clock
Stabilization of X1 oscillation
• OSCSEL = 1, EXCLK = 0, MSTOP = 0
• After elapse of oscillation stabilization time
After checking that the CPU clock is
switched to the clock after change,
operating current can be reduced
by stopping high-speed on-chip
oscillator (HIOSTOP = 1).
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
External subsystem
clock
Enabling input of external clock from the
EXCLKS pin
• OSCSELS = 1, EXCLKS = 1, XTSTOP = 0
X1 clock
High-speed on-chip
oscillator clock
Enabling oscillation of high-speed on-chip
oscillator
• HIOSTOP = 0
• After elapse of oscillation stabilization time
After checking that the CPU clock is
switched to the clock after change,
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
After checking that the CPU clock is
switched to the clock after change,
X1 oscillation can be stopped
(MSTOP = 1).
External subsystem
clock
Enabling input of external clock from the
EXCLKS pin
• OSCSELS = 1, EXCLKS = 1, XTSTOP = 0
External main
system clock
High-speed on-chip
oscillator clock
Enabling oscillation of high-speed on-chip
oscillator
• HIOSTOP = 0
• After elapse of oscillation stabilization time
After checking that the CPU clock is
switched to the clock after change,
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
After checking that the CPU clock is
switched to the clock after change,
external main system clock input
can be disabled (MSTOP = 1).
External subsystem
clock
Enabling input of external clock from the
EXCLKS pin
• OSCSELS = 1, EXCLKS = 1, XTSTOP = 0
Summary of Contents for RL78/G1H
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