7220 Datasheet, PDF (128/303 Pages) Renesas Technology Corp – 8-BIT SINGLE-CHIP MICROCOMPUTER

FUNCTIONAL DESCRIPTION
2.17 Oscillation circuit
2.17 Oscillation circuit
The M37221M6-XXXSP/FP has a internal oscillation circuits used to obtain the clocks required for operation.
Ordinarily, the frequency on clock input pin XIN divided by 2 is the internal clock (internal timing output) φ.
A quartz-crystal oscillator or ceramic resonator can be connected externally to these circuits.
(1) Oscillation circuit using a quartz-crystal oscillator or ceramic resonator
Figure 2.17.1 shows the circuit example using a quartz-crystal oscillator or a ceramic resonator. As
shown in the diagram, oscillation circuit can be constructed by connecting a ceramic resonator (a
quartz-crystal oscillator) between pins XIN and XOUT. In this case, set the circuit constants for CIN and
COUT to the values recommended by the resonator manufacturer.
(2) External clock oscillation circuit
Supplying an external clock is possible, Figure 2.17.2 shows the circuit example.
M37221M6-XXXSP/FP
XIN
19
XOUT
20
CIN
COUT
M37221M6-XXXSP/FP
XIN
19
XOUT
20
Open
External oscillation circuit
VCC
VSS
Note: In the stop mode, keep the XIN pin input
signal at an “H” level.
Fig. 2.17.1 Clock oscillation circuit using a ceramic Fig. 2.17.2 External clock input circuit example
resonator
The M37221M6-XXXSP/FP has a CRT display clock
oscillation circuit, so that display clock can be obtained
simply by connecting a inductor and capacitor between
pins OSC1 and OSC2. Figure 2.17.3 shows the circuit
example.
Refer to “2.11.9 Clock for display.”
M37221M6-XXXSP/FP
OSC1 OSC2
24
23
L
C1
C2
Fig. 2.17.3 Clock oscillation circuit for CRT display
7220 Group User’s Manual
2-101