A two-chip circuit which connects to the parallel printer port of an IBM PC or compatible computer provides 16 TTL-compatible i/o lines which are programmable in 4 groups of 4 bits. A short program in Turbo Pascal is given as an example of how to program the interface. The circuit can be expanded at the cost of one additional chip per 16 i/o bits.source

The purpose of this project was to create a useful yet easy to build Logic Analyzer that would provide much of the functionality of a real Logic Analyzer. The biggest drawback that the computer has is its sampling rate. The program was written on a 75 MHz Pentium computer which provided accurate sampling rates up to 10 kHz. Although this doesn’t match the speed of real Logic Analyzers, this should be sufficient speed to be useful for many projects. source

Here is an ISA bus I/O card circuit for IBM PC compatible.This interface card is controlled by an 8255A Programmable Peripheral Interface I.C.The parallel interface requires 4 bytes of addressing and may be jumpered to recognize one of 64 address groups beginning with &H200,ending with &H2FC.source