Thursday, May 21, 2009

That damn flippity flop music

Otherwise known as flip-flops - these are handy structures that store 1 bit of information - a 1 or a 0. Imagine 8 of them put together and BAM - 1 byte of memory, or imagine 8589934592 and again, BAM, a gig of memory!. So I dont really need much memory for my application as it is all going to be controlled by a laptop which has its own memory anyways. What I do need, though, is a way of remembering if a button has been pressed or not in hardware. This is because (and i cant remember if i talked about this earlier) i cant guarantee that ill be checking the state of a switch while it is actually pressed, so the next best thing is to work out if it was pressed.

Now theres a heap of different flip flops that one can use: SR (set-reset), JK (not sure what that stands for) and more. I have elected to go with an SR type flip flop, which I made myself out of a couple of NAND gates. I reccomend spending some time on this site: http://www.falstad.com/circuit/e-index.html learning how stuff works. If you check out the SR flipflop (unclocked) on that site, youll see a part of the circuit im creating.

So i couldnt find any SR flipflops in a handy dandy IC package so i decided to make my own out of the heap of nand gates i had lying around. I got a little lazy and decided to do it all on a breadboard.Breadboarded NANDS to make flip-flops

Those wires hanging off are going to be terminated with a standard 40 pin IDE cable, and connected on to the actual input board (more about which later).

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