Chapter 6. Clock Generation Circuit - Renesas M16C Series Hardware Manual

R8C/11 Group
6. Clock Generation Circuit
The clock generation circuit contains two oscillator circuits as follows:
• Main clock oscillation circuit
• On-chip oscillator (with oscillation stop detection function)
Table 6.1 lists the clock generation circuit specifications. Figure 6.1 shows the clock generation circuit.
Figures 6.2 to 6.4 show the clock-related registers.
Table 6.1 Clock Generation Circuit Specifications
I t e m
• C P U c l o c k s o u r c e
U s e o f c l o c k
• P e r i p h e r a l f u n c t i o n
c l o c k s o u r c e
C l o c k f r e q u e n c y 0 t o 2 0 M H z
• C e r a m i c r e s o n a t o r
U s a b l e o s c i l l a t o r
• C r y s t a l o s c i l l a t o r
X
P i n s t o c o n n e c t
IN
o s c i l l a t o r
Present
Oscillation starts
and stops
Stopped
Oscillator status
after reset
Externally derived
Other
clock can be input
N O T E S :
1 . C a n b e u s e d a s P 4
c i r c u i t i s n o t u s e d .
Rev.1.20 Jan 27, 2006
REJ09B0062-0120
Main clock
oscillation circuit
, X (1)
OUT
a n d P 4 w h e n t h e o n - c h i p o s c i l l a t o r c l o c k i s u s e d f o r C P U c l o c k w h i l e t h e m a i n c l o c k o s c i l l a t i o n
6 7
page 29 of 204
O n - c h i p o s c i l l a t o r
H i g h - s p e e d o n - c h i p o s c i l l a t o r
• C P U c l o c k s o u r c e
• P e r i p h e r a l f u n c t i o n c l o c k s o u r c e
• C P U a n d p e r i p h e r a l f u n c t i o n
c l o c k s o u r c e s w h e n t h e m a i n
c l o c k s t o p s o s c i l l a t i n g
Approx. 8 MHz
(Note 1)
Present
Stopped
6. Clock Generating Circuit
Low-speed on-chip oscillator
• CPU clock source
• Peripheral function clock source
• CPU and peripheral function
clock sources when the main
clock stops oscillating
Approx. 125 kHz
(Note 1)
Present
Oscillating