RL78/G1P
CHAPTER 5 CLOCK GENERATOR
R01UH0895EJ0100 Rev.1.00
123
Nov 29, 2019
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.
Table 5-4. Changing CPU Clock
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
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.
External main
system clock
Enabling input of external clock from the
EXCLK pin
OSCSEL = 1, EXCLK = 1, MSTOP = 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
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
Transition not possible
External main
system clock
High-speed on-
chip oscillator
clock
Oscillation of high-speed on-chip oscillator
HIOSTOP = 0
After elapse of oscillation stabilization time
External main system clock input can be
disabled (MSTOP = 1) after checking that
the CPU clock has been switched to the
clock after transition.
X1 clock
Transition not possible