Transistor oscillator driving 2 micros - 4 MHz

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atferrari

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Initially I implemented a 4 MHz clock driving 2 PIC micros, using 2 inverters, one of them as a buffer (74HC04). To avoid the waste of space (the other 4 gates do nothing) I tried a transistor oscillator and buffer from an ARRL book but couldn't have it working. In my implementation space is at a premium.

Can anyone show me a really working circuit?

BTW: input should be a 4 MHz square wave or kind of a sine wave? If so, what pk to pk value? No experience on this.

Thanks for any help.
 
Why would you want to do it that way?

Just use a small 4MHz crystal on the first PIC and couple the OSC2 clockout signal to the OSC1 Clockin of the remaining PIC. Job done.
 
I agree. Some of the ICD2 USB clone designs are using a single crystal for both the 18F4550 and 16F877A.

Regards, Mike
 
I didn't know it was possible

I always believed that Clockout pin was giving valid output when Clock1 input pin was receiving an external clock signal only and it was always 1/4 of the inputl.

I wil try that.

My question: does it work with any PIC?
 
atferrari said:
I always believed that Clockout pin was giving valid output when Clock1 input pin was receiving an external clock signal only and it was always 1/4 of the inputl.

I wil try that.

My question: does it work with any PIC?
Click to expand...

As far as I know it does, there was a VERY old technical bulletin that showed how to do it, but it seems to have disappeared now.
 
I always believed that Clockout pin was giving valid output when Clock1 input pin was receiving an external clock signal only and it was always 1/4 of the inputl
Click to expand...
Usually this is the case when you use the internal oscillator, which begs the question:
"Why don't you use the internal oscillator?"
L.Chung's idea is the best if none of your PICs has an internal oscillator option. This is because in the LP, XT & HS MODES the OSC1 and OSC2 pins have an inverter between them which forms the active device for your oscillator. All you are doing is feeding the output of the crystal oscillator of one pic into the inverter of the 2nd one which doesn't have an xtal.
BTW, which PICs are you using?
 
Decision taken

"Why don't you use the internal oscillator?"

Because I want to have a more or less precise clock. I plan to run two sinusoidal generators (one PIC micro each) driven by the same clock.

Have recently modified a design with a 16F84A (yes I know, replaced in the last century, which works quite well).

I will use the option of clokout to clokin.

Thanks for replying to all who did!!!
 
I'm confused.. The internal RC oscillator on a PIC is likley to be more stable than what you're describeing..
 
Sceadwian said:
I'm confused.. The internal RC oscillator on a PIC is likley to be more stable than what you're describeing..
Click to expand...

Why would the internal RC osillator be more stable than a crystal one?.
 
I was refering to the original post. Which didn't mention the use of a crystal, only what I thought was being described as an inverted buffer oscillator using a resistor and a capacitor. Didn't realize this was the external drive of a crystal, if this is so why bother? A lot of pic models have internal crystal drivers, which only require the crystal itself and a pair of low value capacitors.
 
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