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¡ Semiconductor

MSM80C85AHRS/GS/JS

You may drive the clock inputs of the MSM80C85AH with a crystal, or an external clock source.

The driving frequency must be at least 1 MHz, and must be twice the desired internal clock

frequency; hence, the MSM80C85AH is operated with a 6 MHz crystal (for 3 MHz clock). If a

crystal is used, it must have the following characteristics:

Parallel resonance at twice the clock frequency desired

Drive level: 10 mW

Frequency tolerance:

±0.05% (suggested)

assure oscillator startup at the correct frequency.

Figure 4 shows the recommended clock driver circuits. Note in B that a pull-up resistor is

required to assure that the high level voltage of the input is at least 4 V.

For driving frequencies up to and including 6 MHz you may supply the driving signal to X, and

Note:

Since the constant values may vary depending on oscillator, consult the manufacturer

of the oscillator used when designing a circuit.

Figure 4 Clock Driver Circuits

High time > 40 ns

Low time > 40 ns

33 pF Capacitor required for crystal frequency 10 to 6.25 MHz

50 pF Capacitor required for crystal frequency 6.25 to 4 MHz

100 pF Capacitor required for crystal frequency <4 MHz

MSM80C85AH

A. Quartz Crystal Clock Driver

B. 1 - 10 MHz Input Frequency External

Clock Drive Circuit

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