CLOCK GENERATING CIRCUIT
4.1 Oscillation circuit examples
4.1 Oscillation circuit examples
To the oscillation circuit, a ceramic resonator or a quartz-crystal oscillator can be connected, or the clock
which is externally generated can be input. Oscillation circuit examples are shown below.
4.1.1 Connection example with resonator/oscillator
Figure 4.1.1 shows an example where pins X
IN
and X
OUT
connect across a ceramic resonator/quartz-crystal
oscillator.
The circuit constants such as R
f
, R
d
, C
IN
, and C
OUT
(shown in
“Figure 4.1.1”)
depend on the resonator/
oscillator. These values shall be set to the values recommended by the resonator/oscillator manufacturer.
M37906
X
IN
X
OUT
R
f
R
d
C
IN
C
OUT
Fig. 4.1.1 Connection example of resonator/oscillator
4.1.2 Externally generated clock input example
Figure 4.1.2 shows an input example of a clock which is externally generated. An external clock must be
input from pin X
IN
, and pin X
OUT
must be left open.
When an externally generated clock is input, the power source current consumption can be saved by the
stop of internal circuit’s operation between pins X
IN
and X
OUT
. (Refer to
“CHAPTER 16. POWER SAVING
FUNCTION.”)
M37906
X
IN
X
OUT
Open
Externally generated clock
Vcc
Vss
Fig. 4.1.2 Externally generated clock input example
4-2
7906 Group User’s Manual Rev.2.0
RENESAS [ RENESAS TECHNOLOGY CORP ]
