UPD78F1502AGK-GAK-AX Datasheet, PDF (264/1031 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcontrollers

78K0R/Lx3
CHAPTER 5 CLOCK GENERATOR
CPU Clock
Before Change After Change
Subsystem
clock
Internal high-
speed
oscillation clock
X1 clock
External main
system clock
20 MHz internal
high-speed
oscillation clock
20 MHz internal
high-speed
oscillation clock
Internal high-
speed
oscillation clock
X1 clock
External main
system clock
Subsystem
clock
Table 5-5. Changing CPU Clock (2/2)
Condition Before Change
Processing After Change
Oscillation of internal high-speed oscillator
and selection of internal high-speed
oscillation 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
EXCLK pin and selection of high-speed
system clock as main system clock
• OSCSEL = 1, EXCLK = 1, MSTOP = 0
• MCS = 1
Transition cannot be performed unless the
clock is changed to the internal high-speed
oscillation clock once.
• SELDSC = 0
(Set when changing the clock.)
XT1 oscillation can be stopped (XTSTOP
= 1)
−
20 MHz internal high-speed oscillation
clock can be stopped (DSCON = 0)
Transition cannot be performed unless the
−
clock is changed to the internal high-speed
oscillation clock once.
Transition cannot be performed unless the
−
clock is changed to the internal high-speed
oscillation clock once.
Transition cannot be performed unless the
−
clock is changed to the internal high-speed
oscillation clock once.
R01UH0004EJ0501 Rev.5.01
248
Jun 20, 2011