Digital I/O Cards
The circuits use an 82C55A PPI with mode 0 supported. Ports A, B and C are buffered with 74ABT245 transceivers and pulled up to 5V.
The optional 82C54 has three-sixteen bit down-counters within one chip. These counters are useful for making frequency outputs, measuring frequency of square waves, pulse width outputs, pulse width measurements etc. Software drivers are provided on CD.