Multi SX per Oscilator

lboucher

Hi All

So this may or may not be a stupid question.
I am going to make a prototype with 3 dip SX's.
They will all be co-located and co-powered.
Can drive 3 SX dips with 1 50 MHZ oscilator?

Thanks

JonnyMac

I think you need to use a "can" type oscillator, not a standard 3-pin resonator.

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Jon McPhalen
Hollywood, CA

T&E Engineer

I bought a 75 MHz 4 pin metal can oscillator from Parallax a year or so back but dont remember this in 50 MHz.

PJMonty

I agree with Jon Williams that a TTL oscillator is required to drive multiple SXs. However, when I went looking for a TTL through hole oscillator about a year ago, I found it impossible to get one at 50 MHz. They used to be available, but I was unable to find one at the usual sources (Mouser, DigiKey, etc). Ultimately I ended up having to use a surface mount part. If you're making a PCB, it's really not a big deal to solder it as it's only a 4 pin device. If you're point to point soldering a prototype (or using a breadboard), you could simply solder some short wires to it and that would work as well.

One thing to note - if you use a TTL style oscillator, make sure you have a jumper to disconnect the clock output between the TTL oscillator and the SX. Do not count on using the enable pin. Why? Because if you disable the clock and then try and program the chip, the SX Key will not be able to generate teh programming voltage due to output diode protection on the oscillator.

Thanks,
PeterM

wass

You can still buy 50MHz thru-hole oscillators with TTL level outputs:

search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CTX759-ND

-Katie

PJMonty

Katie,

I forgot that I could still get them in the oversize metal cans. The ones I was looking for were in a standard plastic DIP package. The metal cans take up too much PCB space. Of course, now that I'm comfortable with the surface mount parts, even the plastic DIP case is too big.

Thanks,
PeterM