Datasheet

RL78/L12 CHAPTER 5 CLOCK GENERATOR
R01UH0330EJ0200 Rev.2.00 164
Dec 13, 2013
5.6.5 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 5-4. 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
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
Oscillation of high-speed on-chip oscillator
• HIOSTOP = 0
• After elapse of oscillation accuracy
stabilization time
X1 oscillation can be stopped (MSTOP = 1).
External main
system clock
Transition not possible
(To change the clock, set it again after
executing reset once.)
−
XT1 clock
Stabilization of XT1 oscillation
• OSCSELS = 1, EXCLKS = 0, XTSTOP = 0
• After elapse of oscillation stabilization time
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
X1 oscillation can be stopped (MSTOP = 1).
External main
system clock
High-speed on-
chip oscillator
clock
Oscillation of high-speed on-chip oscillator
• HIOSTOP = 0
• After elapse of oscillation accuracy
stabilization time
External main system clock input can be
disabled (MSTOP = 1).
X1 clock
Transition not possible
(To change the clock, set it again after
executing reset once.)
−
XT1 clock
Stabilization of XT1 oscillation
• OSCSELS = 1, EXCLKS = 0, XTSTOP = 0
• After elapse of oscillation stabilization time
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
External main system clock input can be
disabled (MSTOP = 1).