Help need with LPT port, Trying to make a LAPLINK Program

apar...@aol.com (Apartow)

Delphi Developer

Wed, 18 Jun 1902 08:00:00 GMT

Help need with LPT port, Trying to make a LAPLINK Program

I need some help with the lpt port, I'm trying to make a Laplink program.
I know how to get the port and send data to them, Or I think I do but I can
seem to get the data onto the other computer.

Please Please Please if anyone knows how to do please give me a mail.

Arash Partow

Ing. Franz Glase

Delphi Developer

Wed, 18 Jun 1902 08:00:00 GMT

Re:Help need with LPT port, Trying to make a LAPLINK Program

Quote

Apartow wrote:

> I need some help with the lpt port, I'm trying to make a Laplink program.
> I know how to get the port and send data to them, Or I think I do but I can
> seem to get the data onto the other computer.

There are several points to be considered. The most important is: the
standard printer port on the IBM-PC is a rather silly circuit (like most
on the IBM-PC). The 8-bit data port is unidirectional, it can be used to
output a byte only, but cannot read a byte. Reading at 378H simply gives
the last byte back, which you sent before.

On newer PC-clones there are improvements, but - as usual, several
distinct standards were introduced that are incompatible.

If you want to make a program that shall work on ANY brand of PC, you
will have to reduce to the minimum, and that is the PC standard.

With the PC standard there are only 4 input bits available in the status
port, like ACK and ERROR and PAPER TRAY EMPTY. You will have to squeeze
the data bytes into 4-bit nibbles, and even this is too much if you
would like to have a proper handshake, which occupies at least
received 1 bit.

Look in the TP-links, chapter "serial", there is a sub-chapter for the
parallel port.
http://www.geocities.com/SiliconValley/2926/tp.html

Regards, Franz Glaser

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