>the first diagram is used by FastWire software:
>
>Bit 0       2       -------->       15      -Error
>Bit 1       3       -------->       13      Select
>Bit 2       4       -------->       12      P End
>Bit 3       5       -------->       10      -ACK
>Bit 4       6       -------->       11      Busy
>-ACK        10      <--------       5       Bit 3
>Busy        11      <--------       6       Bit 4
>P End       12      <--------       4       Bit 2
>Select      13      <--------       3       Bit 1
>-Error      15      <--------       2       Bit 0
>GND         18-25   ---------       18-25   GND
>
>this set of connections (i will call it as STANDARD), uses
>unidirectional flow of signals, that is, bit 0, bit 1, bit 2,
>bit 3 and bit 4, are output signals, while, ack, busy, pend,
>select and error, are input signals. then this STANDARD set of
>connection allows 5 bits full duplex channel (4 data bits & 1
>handshaking bit ?????)

The above cable is the only one I've tried (being the only one I've heard of)
And I do believe it is using 4 data bits and 1 handshaking on each side. This
would allow "full-duplex" communication in both directions at the same time.
(although only 4-bits at a time)

>QUESTION:
>is there some new PC standard which allows use the LPT port signals
>stb, autofeed, init prn and slct, as input/output? if there is not
>such standard, is it common to find PC's which allow that option?
>which port signals allow input/output?

In the old days all ports were originally bidirectional. Most using the
6821, 6521, or the 8521 which is different manufacturers equivilent of
a PIA or Peripheral Interface Adapter. Only later did IBM and a few
others try to get cheap and set them up as output only to the printer
with only a busy signal being sent back to the printer. All PIA chips
have two 8-bit bi-directional ports and two interrupt lines (one for each
8-bit port) No a days "they" are trying to get back to the original bi-
directional port.

>of couse, as far as all the cables have the STANDARD SET of 5 bits,
>which work uni-directionally, with the old standard of
>lpt port, i think that all software run ok, at least, with the worse
>condition of 5 bits.
>
>then, i think, that software can test first if the connection has
>bidirectionality, that is, if the PC HAS BIDIRECTIONAL PORTS AND THE
>CABLE IS THE CORRECT ONE FOR THIS SOFTWARE, then the software may work
>faster, if not, then it will work, but slowly with only 5 bits.
>
Even with only 4-bits and a fifth for flow-control, it'll be four times
faster than
the highest speed serial connection of 115000 bps.


>i will appreciate very much comments on this topic, also, i would like
>to know, which standard of cable uses Win95 for Direct Cable
>Connection, in order to allow the maximum speed, if the PC allows
>input/output signals in LPT port.
>
>gary
>
This may be a little too limited for but then again it may be just enough to
get you started in the right direction.

Winston


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