Comic Genesis Forums

Latches and Flipflops:

The design of digital circuitry is the design of machines for pushing zeroes and ones around. But after all that pushing zeroes and ones around is done, you have to put them somewhere.

A latch is a place you can put a zero or a one. Imagine a box with three wires sticking out of it. Let's call these wires the "in" "out", and "control" wires.

Now suppose I may connect a battery to either the "in" or "control" line (a one) or not (a zero). Here's a table of what happens:
That's really all there is to it. The diagrams you might see of cross-coupled NAND gates and so on are just to give students an idea of how such things might be made (although in real circuits, these devices are -rarely- made by cross-coupling gates)

Flipflops are just pairs of latches in series, with the "control" lines always forced to be opposite one another. If you work it out on paper, you should be able to see that these gizmos actually "sample" the input at the moment the "control" lines switch. These are called "edge-triggered" storage devices, and they are -very- common, particularly in microprocessors like the ones in your computer, calculator, or toaster.

(They'll put microcontrollers in ANYTHING these days!)

maximuscoolman wrote:So I run a search for latch and flipflop and get stuff like this, then I smile, nod, and click of the topic slowly.

When you say "Flip Flop", I think of this.

I once painted a Q on one sandal and a Q with a bar over it on the other and put them up on my desk at the beginning of digital systems class.

My instructor just about fell over.

DetailBear wrote:

maximuscoolman wrote:So I run a search for latch and flipflop and get stuff like this, then I smile, nod, and click of the topic slowly.

When you say "Flip Flop", I think of this.

oy.

It's not his superior knowledge I mind,

but again he mocks me with his hipper taste in music.

*goes back to looking for an Aretha cover of Stairway to Heaven*

Correct me if I am wrong, but if memory serves I believe one of the very first (if not the first) commercially available ICs was a flip flop...

I think that was made by Fairchild Semiconductor...

As for Tek, I feel old as I look over the screen of my computer at the Type 547 scope on its floor standing cart that's sitting next to my video monitor. It's huge, and it actually uses tubes. But with the (kinda sorta almost) dual timebase I can mostly manage to get it to sync to colorburst in an NTSC waveform and then dial in to some useful parts of the signal.

Oh and it's cool to hook the thing up to my synths and watch what I am doing when I try to play around making nifty sounding patches

On completely unrelated tet equipment matters: Anybody know where I can get a really cheap vectorscope?

If by vectorscope, you mean logic analyzer, I understand they make data acquisition cards for PCs. A few hours of schematic work (and a couple of days worth of coding) could pay off with a half-decent logic analyzer for a fraction of what you'd have to pay for a Tek analyzer.

Donno. Maybe I'll look into it..

Actually I was thinking of the gizmo used to analyze video signals. You feed NTSC into it, and use it to analysize aspects of the signal, like relative color intensity, signal strngth and the like. Especially useful when you consider the truly perverse things NTSC does to color...

It's especially useful when you point a pair of cameras at identical subjects (grey or white cards) and you can then use the vectorscope to adjust things like camera color balance and other things to match up your camers to each other so when you do edits and cuts between two signals you more or less get the same color balance from both sources.

You can do a whole bunch more with one of those too.

A wonderful gadget to have if you're trying to do anything with video gear.

They do make PC cards that are essentially vectorscope in a slot things, but I'd rather try to find an ultra cheap bit of used kit that is dedicated...

OOOOOOOOOoooooooooooooo.

Tek makes those, but they're more the high-end variety. They're telling me these suckers can detect erroneous lip-synch.

Dood.

Ever see that one episode of Freakaziod where the lipsynch goes bad for a few seconds, and Frekazoid says "Sheesh, let's watch the lipsynch, alright?"

A giant pair of lips is depicted sinking into the ocean like a punctured cruise vessel, after which point, the F-man says "Ah, thank you." Brutal.