Originally Posted by rainbow

hi all
i have a problem with the parallel port ( exactly with status pins)

i implement an adc using (dac , comparator and a simple software of succusive approximation)
i use an lm741 as a comparator with 12v-ground.
when comparator is high output=9.8v
when comparator is low output=1.89v
this output must be connected to status through parallel port
comparator is either high or low, the status pin don t change its output,it has an output of 4.7v (for only one pin of course ).
is this because of low power from my circuit?
my circuit could not change the pin votage???
when i have connected the ground of the circuit tothis pin it changed to low
but it dont response to my comparator (lm741).......
what is my fault ....?? please it is important for my project

hint:sorry if my english is bad or there is some errors

Originally Posted by ericgibbs

hi,
It looks as though the 741 otput is not going low enough to switch the status pin low. Not a logic '0'
i use a seris resistanse to have a drop on it but it didnt work the status pin is still 4.7v
Do you have another comparator, a LM393 for example.????

Do not appy 9.8V to the status pin, it will damage the port.

Originally Posted by rainbow

first thanks for replying



i did it actually but it turned to 4.7v (the original output of the status pin i use)

Originally Posted by ericgibbs

hi Menticol,
Attached zip file is for:

MC3202 dual 12bit ADC


EDIT: Added a screen shot.

Originally Posted by Menticol

Sorry by double-posting, edit was disabled

Working with 74LS139 By now, I know how to cascade two of them

But how can I cascade 3, or more?

Thank you in advance