Re:Direct parallel port access in Delphi
Quote
UNiDoG wrote:
> Hi,
> I'm writing a program that needs to access the parallel port's datalines. It
> needs to reads the databits and set them, so they remain at the same
> position even after the program stopped. It's for use with a parallel port
> relay.
> Does anyone know how I can direct access the port ??
> Thanks in advance,
> Kim
Delphi 3 doesn't offer any port handlers that I could find. My solution is to
use an ASM block to write and read straight from
the io port.
procedure WriteByte(myb : byte);
begin
asm
mov al, myb {byte to write}
mov dx, $378 {address to write to, lpt1 here}
out dx, al
end;
end;
swap out 'out dx, al' with 'in dx,al' and remove the 'mov al,myb' to read the
port.
remember that the port reads back the line levels or'd with the last writen
value to the port. You might want to write a $00
to $378 then read it to get the true values.
Also, this only works in '95 ('98?), not NT. NT will hurl protection errors at
you when it runs.
Good luck
Thomas Kreider
tkrei...@uswest.net
