Normally in micro computer system will use a crystal as frequency generator. Although now the crystal will be cheap down. But then still is an expensive components,when compared to other devices.
And I like to modify the electronic devices that remove from the old PCB to reused always. Because it enables us to save. And reduce environmental problems as well.
I checked the old board about radio receivers. usually found one interesting device is a ceramic filters. It could replace the crystal. Help us to save, and electronic skills also improved.
In the production of high frequency. Digit numbers behind Of frequencies is rarely important. However, the need for precision is stability. Which the ceramic filters has this feature. From circuit
As circuit shown can Can produce precisely the frequency of 1.07 Mhz Therefore, applied to micro-processor.
The circuit consists of the generators section are N1,N2,P1,R1 and ceramic filters. The output is sent to N3 inverter to makes a waveform to more beautiful. Then forwarded to the input B of IC2. which is counting base 10. While the output QD signaling back to input A. The output frequency from QA will be 1 in 10 of the frequency generator.
(N1,N2,N3 = 74LS04 as inverter gate TTL IC)
IC2-74LS90 can also be counter circuit 5:1 as well. Which will be has the output frequencies is 2.14 MHz. To use for CPU number Z80 or ceramic filters are applied to the 455 Khz optional. But should be P1, so that the low-frequency stability better. And the output frequency is 45.5 Khz (or, if divided by 90.1 Khz 5:1).
However If you think that this circuit is not good enough for you.
You can see the crystal circuit is as follows:
1. Crystal oscillator circuit
2. Crystal oscillator using TTL
3. 1HZ Standard digital clock
4. The 60hz calibration frequency standards for digital clock by MM5369
5. Pulse Generator Oscillator 32.768KHz by watch crystal
6. Oscillator astable multi-vibrator with Crystal controller
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