martin.shoebridge ha scritto:
> I thought ISO cards work on a byte basis with CK + Data. Is this card
like
> that or something completely different? Even if it's on a byte basis (
> rs232) then you can tolerate at least a few% error......
Sorry, I don't understand what you mean by "on a byte basis", In the
case I'm dealing with the data are treated in two different ways
depending on their direction...
data from reader to card is serially ****fted a COUPLE bit a time, on a
1-of-4 pulse position scheme. this transmission scheme is not
self-clocking, it is asynchronous and relies on the timing accuracy
between transmitter and receiver... even a small error may get bigger
and bigger as the data frame is received, up to the point of mistaking
bit positions.
Data from card to reader is manchester-encoded, a logic 0 is a space
followed by a mark, a logic 1 is a mark followed by a space..that
strategy makes the protocol self-clocking and in this case a timing
accuracy is not so strictly necessary..
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