Condition Before Changing Cpu Clock And Processing After Changing Cpu Clock - Renesas RL78/G1P Hardware User Manual

RL78/G1P

5.6.4 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
High-speed on- X1 clock
chip oscillator
clock
External main
system clock
X1 clock High-speed on-
chip oscillator
clock
External main
system clock
External main High-speed on-
system clock chip oscillator
clock
X1 clock
R01UH0895EJ0100 Rev.1.00
Nov 29, 2019
Table 5-4. Changing CPU Clock
Condition Before Change
Stabilization of X1 oscillation
 OSCSEL = 1, EXCLK = 0, MSTOP = 0
 After elapse of oscillation stabilization time
Enabling input of external clock from the
EXCLK pin
 OSCSEL = 1, EXCLK = 1, MSTOP = 0
Enabling oscillation of high-speed on-chip
oscillator
 HIOSTOP = 0
 After elapse of oscillation stabilization time
Transition not possible
Oscillation of high-speed on-chip oscillator
 HIOSTOP = 0
 After elapse of oscillation stabilization time
Transition not possible
CHAPTER 5 CLOCK GENERATOR
Processing After Change
Operating current can be reduced by
stopping high-speed on-chip oscillator
(HIOSTOP = 1) after checking that the CPU
clock has been switched to the clock after
transition.
X1 oscillation can be stopped (MSTOP = 1)
after checking that the CPU clock has been
switched to the clock after transition.

External main system clock input can be
disabled (MSTOP = 1) after checking that
the CPU clock has been switched to the
clock after transition.

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