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CHAPTER
5 C
L
OC
K
GENERA
TOR
User’s Manual
U1
9780EJ2V0UD
129
Figure 5-1. Block Diagram of Clock Generator (78K0/KB2-A)
Option byte
1: Cannot be stopped
0: Can be stopped
LSRSTOP
RSTS
RSTOP
f
RL
Peripheral
hardware
clock (f
PRS
)
Watchdog timer,
8-bit timer H1
CPU clock
(f
CPU
)
Processor clock
control register
(PCC)
PCC2 PCC1 PCC0
f
XP
X1 oscillation
stabilization time counter
OSTS1 OSTS0
OSTS2
Oscillation stabilization
time select register (OSTS)
3
MOST
16
MOST
15
MOST
14
MOST
13
MOST
11
Oscillation
stabilization
time counter
status register
(OSTC)
MCM0
XSEL
MCS
MSTOP
STOP
EXCLK OSCSEL
AMPH
Clock operation mode
select register
(OSCCTL)
3
f
XP
2
f
XP
2
2
f
XP
2
3
f
XP
2
4
Main clock
mode register
(MCM)
Main clock
mode register
(MCM)
Main OSC
control register
(MOC)
f
RH
Internal bus
Internal bus
High-speed system
clock oscillator
Crystal/ceramic
oscillation
External input
clock
X1/P121
X2/EXCLK
/P122
f
XH
f
X
f
EXCLK
System
clock switch
Peripheral
hardware
clock switch
Controller
Prescaler
Selector
Internal oscillation
mode register
(RCM)
Internal low-
speed oscillator
(240 kHz (TYP.))
Internal high-
speed oscillator
(8 MHz (TYP.))