On Thu, 3 Jan 2002, Baltissen, R (Ruud) wrote:
> Hallo Sam,
>
> > http://www-uxsup.csx.cam.ac.uk/~bjh21/BBCdata/MC6854.pdf
>
> Thanks for the link.
>
> > No, it was chained. Very thin looking cable I recall, maybe
> > as few as 4 wires (I am assuming arranged as twisted pair
> > or something).
>
> There are 2 connectors on the card with 4 pins each. Haven't checked what
> they are. And about the drivers, the only "strange" IC was this 6854, the
> rest were common TTL ICs IIRC. But not having the card here right now, I
> cannot say if the lines are driven by OC outputs or whatever.
HDLC/SDLC would have a receive, transmit, clock, and ground. Synchronous
Data Link Communication is a subset of HDLC. It is a serial protocol that
transmits and receives simultaneously with separate transmit and receive
lines, so that no pauses are needed between packets of data. No
synchronization protocols are needed as the data is synchronized by an
external clock, supplied by one of the connected devices. SDLC can have
control lines like a standard asynchronous serial connection, but
these are not really needed since the control functions do not change
once the connection is established.
Two connectors on a card probably indicate a feed-through for the next
device on the line.
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