The table and the signal function of each pin on the parallel printer port, shown in Figure 2. From there the pin 2 s / d 9 (signal D0-D7) as a function of output, then we can take advantage of to control the external equipment.
Of the scheme in Figure 4, visible pins 3,5,7,9,12,16 and 18
of the 74LS224 is connected to each relay. Next
switch on each of these relays, we can use to
control equipment that has a big burden.
Delphi Code Program
Unlike Turbo Pascal or Delphi 1 in which the port is available,
on 32-bit Delphi (version 2 s / d 6) function is not supported anymore.
Instead we use in-line assembler code.
Listing 1. Turn the LED 5 of a series in Figure 3.