From Computer History Wiki
- Your friends are right. Wikipedia uses the confusing 'a flip-flop or latch is..', which is easy to interpret to mean that 'latch' is just another word for 'flip-flop', which is not what is meant. There is a distinction, although there's overlap (b/c there are different types of latches). And when I design something I think of latches and flip-flops as entirely different things (e.g. flip-flops to divide or fix clock signals, latches to buffer/hold data). (Here's a web page which talks about flip-flops vs latches): http://www.electronicsteacher.com/computer-architectures/digital-circuits/flip-flops.php Tor (talk) 09:35, 12 March 2018 (CET)
- In current terminology, the two indeed refer to sets of things which do not overlap. However, after thinking about it (which I hadn't done before :-), I still think it might be appropriate to cover them in one article:
- They are both devices which use feedback to store information
- Separate articles would therefore have a lot of duplication
- Historically (and this is a history wiki :-), the terms were not so carefully delineated; e.g. in Pfister's book (he's the guy who came up with the whole SR/D/JK/T nomenclature), he talks about "R-S flip-flops"
- I will definitely try and make clearer (than it already is) that in contemporary terminology, the two terms refer to disjoint sets. See what you think... Jnc (talk) 14:15, 13 March 2018 (CET)
- Also, the division into flops/latches is not necessarily recent. I looked at the TI TTL data-book, from 1976, and they make the latch/flop distinction there. Jnc (talk) 18:10, 13 March 2018 (CET)
- Yup. In fact, I just recently had confusion talking to my partner on the QSIC project about state storage devices - as part of clearing it up, he introduced me to the 'transparent' terminology.
- But I had a bit of hard time compressing it all into short text. The issue was S-R device, which doesn't have a 'data' input, or a clock, and is not (strictly speaking) 'transparent'! It's too primitive! And the J-K flop, which doesn't have a data input, didn't help! Eventually I resorted to saying 'flops are now so-and-so, everything else is latches'! Jnc (talk) 18:10, 13 March 2018 (CET)
- Alas, in reading about various kinds of flip-flops in the TI TTL reference book, I discovered things are even more complex than I realized! See, e.g. the 7473/6/8 and 74LS73/6/8 - which have different clocking! So I've now added a section which attempts to give a general, systematic framework for understanding flops/latches: when they look at the inputs, etc.
- I hope I've made things better; the text may be more complex now, but alas the reality is complex, and I think I have captured things in a way which makes the complexity easier to grasp. But I'd be interested in feedback! Jnc (talk) 09:52, 15 March 2018 (CET)