From: Jim Brain (brain_at_jbrain.com)
Date: 2007-11-07 05:50:00
David Wood wrote:
> Network: Half-duplex packet-based bus network (think: Model railroad DCC
> system). Collision detection is done by using both serial ports linked
> together: When you transmit a byte, you also recieve it. Transmit, then
> check to see if what yout ransmitted is what was seen on the line. If not,
> there was a collission with another node's data, and you need to retransmit
> your data after a short/random delay. This should be done after each byte
> transmitted of course, so you dont flood the line with a packet full of
> collissions.
>
>
I believe the CIA serial ports are synchronous, so you need the SP1 and
and CNT signal, which makes this harder, as CNT could get mangled if two
machines try to transmit at the same time. On the plus side, CNT and
SP are open drain, so they wouldn't fight each other on the network. It
seems a token passing or some other collision avoidance scheme is
needed. The 64 PRG speaks of using the SP/CNT pins in a network, but
master/slave.
Maybe have a common ATN wire like the IEC protocol? But, how to use it?
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