A very brief overview of parallel port driven home made EPROM programmer. DSCN0481

The data seen in the EPROM being read is the translation table for the ANI for the step switch.
These are just a very few of the surface highlights of my home made
EPROM programmer. It works by using 10 binary bits from the parallel
port. 8 of those bits are for the data which can be anything in the range
from 00 to FF. Then there are two more bits used. One of those bits
acts to increment the address counter on the external programmer circuit,
and the 2nd of those two bits makes the programming pulse that does the loading of the data into the EPROM. All (10) of those bits coming from the
computer's parallel port go straight to 4N35 optocouplers via a 4.7 k
resistor. This assures a very low loading on each port bit and this method also completely isolates the computer's 5 volt supply from the 5 volt supply
used to run the external circuit. The programmer circuit has many options
to enable it to operate many types of EPROMS and other memory types.