6502.org

In Appendix A, "65x Signal Description" of Eyes & Lichty, several signal names have an apostrophe after them. For example, there is:

• IRQ'
• NMI'
• R/W'
• RESET'
• ABORT'
• ML'
• VP'

What does the apostrophe mean? How is it pronounced?

I think the apostrophe is equivalent to the B suffix that is sometimes used, which represents the bar (bar over signal name) shown in diagrams, which indicates an active-low signal.

Where have you seen the B suffix?

It's in all the WDC data sheets. It stands for "bar," and WDC did it because the equipment used to write the early data sheets was not able to put a bar over the various signal names, just as we can't get it here in the forum software (except as an image). So for example , that is, NMI-not, or NMI-bar, got turned into NMIB.

AKA /NMI or ~NMI or !NMI

I guess I can pronounce it "prime" when I see it like that. Thanks. This thread claims to have BBCode for overline but I don't know why it doesn't work when I try it here:

https://www.phpbb.com/community/viewtopic.php?t=2168800

From a logic perspective most pronounce it "not" which is a hugely powerful operator in logic.

In pure binary logic you have 3 operators: "or", "and" and "not". To me, "not" has always given logic its magic. It's the active operator while "and" and "or" are passive operators.

I'm not explaining this well.

I think what you may be trying to say is that a NOT gate has to be able to turn "nothing" into "something" but OR and AND gates simply absorb and combine what's given to them in different ways and forward it to their output?

and vice-versa, where the "something" is a 1 and the "nothing" is a 0. With only passive components (diodes and resistors, and no power supply), you can get AND and OR (albeit with loss, so after a couple of stages you're out of strength to drive anything); but NOT requires active circuitry.

I didn't try the HTML Replacement - I tried the BBCode Usage.