Re: TI-H: fargo fterm
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>
>The internal ROM routines on the 85 (and probably the 92, given that it
>uses the same GRAPH-LINK cable and CBL as the 8x series calculators) use
>one line for DATA and the other line for ACK (which is which depends on
>the bit currently being sent).
Well that's close. Both lines are used to send and receive data. The 'W'
is a "1" and the 'R' is a "0" (I think that is the order). If you send a 1,
the W wire is pulled low. The receiving end acks the bit by pulling the R
low. Then, both ends release both lines to high. This completes the
transmission of one bit. Now if you are sending a 0, the R wire is pulled
low. The receiving end acks the bit by pulling the W low. Then, both ends
release both lines to high again.
>This is not RS232, this is a 2-line async protocol, and it is used on the
TI's for precisely
>the reason above -without a reasonably stable clock, sending RS-232 isn't
generally >possible.
>
Your right, it's not RS-232. RS-232 can be synchromous or asynchronous and
a whole lot more, but I won't get in to that. The TI protocol, IS a
synchronous protocol. Not in the traditional way; using clock signals.
It's synchronous though because, the sender places a bit out there to be
read by the receiver and has to waits for it to be acked before it can send
the next bit. The protocol is synchronous because, the sender is held in
time to the receivers ability to read the bits.
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