A copy of my reply to somebody who asked questions like yours. Hope it helps you .
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Hi!
Wiegand timing is a difficult question. I found one doc ( http://parsek.yf.ttu.ee/~felc/Wiegand2.pdf ) but in reality it looks different and depends much on manufacturers ...ee...fantasy ? Anyway, working principle is always the same, like described in the pdf.
About code. Are the files, mentioned in my postings missing? There should be full Prox reader code for PIC12F629 and essential part for PIC16F628 reading 2 readers simultaneously. Heavily commented.
In assembly, of course

rgds,
/Felch

PS. If you still have questions, drop me a mail
PS. will copy the same contents to forum also, may-be somebody needs it.
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/Felch