Buffer needed?

Jimmy W.

I am planning to use 1 props counter (xtal 6mhz) to output a 6mhz clock to drive 3 other props xin.
2 questions:

1: should I use some sort of buffer to prevent feedback and isolate the xins from each other, or just common bus them right into each other?
2: I was unclear about this, some chips require you to connect xo to gnd, others specify you should let them float, as I am prone to becoming blinded by what is staring me in the face and I might have missed it, which is correct for the prop?


Jimmy

Beau Schwabe

Don't connect the XO to ground!! Since this pin is driven as an output, connecting it to ground would eventually cause damage.

See page 15 of the Propeller manual under XI and XO pin descriptions.



As far as buffering.... this depends more on how far·your 6 MHz signal needs to go and what the signal quality looks like on the receiving end.
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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Post Edited (Beau Schwabe (Parallax)) : 6/20/2008 5:45:40 AM GMT

Jimmy W.

the traces will be cumulatively 105mm, I unfortunately would have to order the boards with or without to be able to look at the signal on the receiving end, if I use a hex buffer with the delay iirc most specs @ 6mhz would put the output 90 degrees out of phase, while this should not be a problem, I would prefer to follow the good old K.I.S.S. strategy.



Jimmy