Datasheet

RL78/L12 CHAPTER 5 CLOCK GENERATOR
R01UH0330EJ0200 Rev.2.00 165
Dec 13, 2013
Table 5-4. Changing CPU Clock (2/2)
CPU Clock Condition Before Change Processing After Change
Before Change After Change
XT1 clock
High-speed on-
chip oscillator
clock
Oscillation of high-speed on-chip oscillator and selection
of high-speed on-chip oscillator clock as main system
clock
• HIOSTOP = 0, MCS = 0
XT1 oscillation can be
stopped (XTSTOP = 1)
X1 clock
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
External main
system clock
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
High-speed on-
chip oscillator
clock
Transition not possible
−
External
subsystem clock
High-speed on-
chip oscillator
clock
Oscillation of high-speed on-chip oscillator and selection
of high-speed on-chip oscillator clock as main system
clock
• HIOSTOP = 0, MCS = 0
External subsystem clock
input can be disabled
(XTSTOP = 1).
X1 clock
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
External main
system clock
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
XT1 clock Transition not possible
−