4 - Channel Digital Logic
Analyzer and 5 Channel Digital Oscilloscope by using PC Parallel Port
source: By Huzaifa S.
This is one of the simplest circuit for a PC parallel port based
DLA. The Circuit is mainly used to protect the port which is fabricated
on the motherboard itself.
The IC 74LS04 is an inverter and acts as a buffer. The Zener is used
for undervoltage and overvoltage protection. If a voltage > 5V appears
on the input, The buffer will not transmit this voltage to the PC. In
the case of a voltage < 0V, The Zener will break down and 0.7V will
appear at the input, hence again protecting the PC.
The software consists of two parts a graphical interface which shows
five digital waveforms,.Various features of the waveforms can be
controlled by the software. There is also a text interface in which the
circuit is used as a 4-Channel DLA. The software is in pascal , an
executable version is also avaliable.