M16C80 Datasheet, PDF (54/358 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/80 SERIES

M16C/80 Group
8. Clock Generating Circuit
8. Clock Generating Circuit
The clock generating circuit contains two oscillator circuits that supply the operating clock sources to the
CPU and internal peripheral units.
Table 8.1 Main clock and sub clock generating circuits
Main clock generating circuit
Sub clock generating circuit
Use of clock
• CPU’s operating clock source • CPU’s operating clock source
• Internal peripheral units’
• Timer A/B’s count clock
operating clock source
source
Usable oscillator
Ceramic or crystal oscillator
Crystal oscillator
Pins to connect oscillator
XIN, XOUT
XCIN, XCOUT
Oscillation stop/restart function Available
Available
Oscillator status immediately after reset Oscillating
Stopped
Other
Externally derived clock can be input
8.1 Example of oscillator circuit
Figure 8.1 shows some examples of the main clock circuit, one using an oscillator connected to the
circuit, and the other one using an externally derived clock for input. Figure 8.2 shows some examples of
sub clock circuits, one using an oscillator connected to the circuit, and the other one using an externally
derived clock for input. Circuit constants in Figures 8.1 and 8.2 vary with each oscillator used. Use the
values recommended by the manufacturer of your oscillator.
Microcomputer
(Built-in feedback resistance)
XIN
XOUT
(Note)
Rd
Microcomputer
(Built-in feedback resistance)
XIN
XOUT
Open
Externally derived clock
CIN
COUT
Vcc
Vss
Note: Insert a damping resistance if required. The resistance will vary depending on the oscillator and the oscillation
drive capacity setting. Use the value recommended by the maker of the oscillator.
When the oscillation drive capacity is set to low, check that oscillation is stable.
Insert a feedback resistance between XIN and XOUT when an oscillation manufacture required.
Figure 8.1 Examples of main clock
Microcomputer
(Built-in feedback resistance)
XCIN
XCOUT
(Note)
RCd
Microcomputer
(Built-in feedback resistance)
XCIN
XCOUT
Open
Externally derived clock
CCIN
CCOUT
Vcc
Vss
Note: Insert a damping resistance if required. The resistance will vary depending on the oscillator and the oscillation
drive capacity setting. Use the value recommended by the maker of the oscillator.
When the oscillation drive capacity is set to low, check that oscillation is stable.
Insert a feedback resistance between XCIN and XCOUT when an oscillation manufacture required.
Figure 8.2 Examples of sub clock
Rev.1.00 Aug. 02, 2005 ^{Page 43} of 329
REJ09B0187-0100