Renesas RL78 Series User Manual page 169

RL78/G1D
CPU Clock
Before Change After Change
XT1 clock High-speed on-
chip oscillator
clock
X1 clock
External main
system clock
External
subsystem clock
External High-speed on-
subsystem clock chip oscillator
clock
X1 clock
External main
system clock
XT1 clock
R01UH0515EJ0120 Rev.1.20
Dec 16, 2016
Table 6-4. Changing CPU Clock (2/2)
Condition Before Change
Oscillation of high-speed on-chip oscillator
and selection of high-speed on-chip
oscillator clock as main system clock
● HIOSTOP = 0, MCS = 0
Stabilization of X1 oscillation and selection
of high-speed system clock as main system
clock
● OSCSEL = 1, EXCLK = 0, MSTOP = 0
● After elapse of oscillation stabilization time
● MCS = 1
Enabling input of external clock from the
EXCLK pin and selection of high-speed
system clock as main system clock
● OSCSEL = 1, EXCLK = 1, MSTOP = 0
● MCS = 1
Transition not possible
Oscillation of high-speed on-chip oscillator
and selection of high-speed on-chip
oscillator clock as main system clock
● HIOSTOP = 0, MCS = 0
Stabilization of X1 oscillation and selection
of high-speed system clock as main system
clock
● OSCSEL = 1, EXCLK = 0, MSTOP = 0
● After elapse of oscillation stabilization time
● MCS = 1
Enabling input of external clock from the
EXCLK pin and selection of high-speed
system clock as main system clock
● OSCSEL = 1, EXCLK = 1, MSTOP = 0
● MCS = 1
Transition not possible
CHAPTER 6 CLOCK GENERATOR
Processing After Change
After confirmation of switching CPU clock to
status before change, XT1 oscillation can
be stopped (XTSTOP = 1)
–
External subsystem clock input can be
disabled (XTSTOP = 1).
–
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