🚀 go-pugleaf

In article <1992Dec14.004912.6491@massey.ac.nz> L.Chisholm@massey.ac.nz (Len Chisholm) writes:
>There is nothing difficult about sending information back from a printer
>to a DEDICATED program. The program says to the printer 'Tell me' and
>then reads a serial bit-stream back from one of the handshake lines,
>perhaps using another as a clock and some form of interlock.
>
>Lap-link etc need special cables to connect the OUTPUT pins of one
>computer to the INPUT pins of the other, whereas the printer already
>has output drivers on the handshake output lines.

If you dissect a Laplink cable, you can actually see that you have 4 pins 
to play with, so it only takes two reads or writes to get a byte instead
of 8.  *However* after dissecting the necessary software we found out 
that, for applications (such as ours) that would require having extra 
logic sent through the parallel port, this would slow things down incredibly.
We needed to send address logic down to some pc boards, followed by some
bytes of data.  The resulting code was something like 50 machine instructions
to simulate what would have been one "in" instruction.  Ferget that. :)

>
>-- 
>-------------------------------------------------------------------------
>|  LEN CHISHOLM , Systems programmer  | EMail: L.Chisholm@massey.ac.nz  |
>| Department of Production Technology | Phone: +64 6 3505262            |
>|         Massey University           | FAX:   +64 6 3505604            |
>|   Palmerston North, New Zealand     |                                 |
>-------------------------------------------------------------------------

Duane Morin
 Software Development Manager
 Walker Sonix, Inc
 Worcester, MA 01604