7220 datasheet(128/303 Pages) RENESAS

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2-101

7220 Group User’s Manual

2.17 Oscillation circuit

Fig. 2.17.3 Clock oscillation circuit for CRT display

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.

Fig. 2.17.1 Clock oscillation circuit using a ceramic

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.”

Fig. 2.17.2 External clock input circuit example

VCC

VSS

External oscillation circuit

Open

XIN

XOUT

M37221M6-XXXSP/FP

In the stop mode, keep the XIN pin input

signal at an “H” level.

Note:

CIN

COUT

XIN

XOUT

M37221M6-XXXSP/FP

OSC1

M37221M6-XXXSP/FP

OSC2

FUNCTIONAL DESCRIPTION

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