Here I go again testing more circuits on two computers with each reporting completely different data yet I feed the same data in.
Now this time, the data coming back is all logic highs on my laptop and on my desktop, more accurate data.
I did read somewhere that older parallel ports were TTL and had internal resistors in them that helped defined their default logic level (I assume my desktop), and I also read somewhere that some parallel ports are open-collector (my laptop?)
The status pins of the parallel port are connected to the outputs of a 74HC157 multiplexer through 100-ohm pull-up resistors.
I also heard about using pull-up or pull-down resistors for the status lines, but I'm not really sure since parallel port technology has changed over the years (heck, the internet has too!).
Should I really use pull-ups (I'm thinking 10K?) and assume the output of 74HC157 is too weak for the parallel port to detect?