What the Shed Looks At

Tuesday, August 18, 2009

A Simple "Memory" Circuit

If "Control" is 1, then this circuit will output the same value as the "Data" input. When "Control" switches to 0, the circuit will retain the value of "Data" at that time and continue to output it indefinitely, ignoring all further "Data" until "Control" is again 1.

A primer on NAND gates

This circuit contains four NAND gates and one NOT gate (which can be implemented by a fifth NAND gate.) If you know of a simpler and/or more economic way to implement the same functionality, please do tell.

Also, I changed the settings so that only the most recent 7 days display on the front page of this blog. I'm open to adjusting that setting further, but I don't like having the entirety of the blog on the front page. My browser was using around 170M, most likely due to all of those youtube embeds.

1 comment:

  1. I wish I remembered my shit from the digital logic classes I took. I lost the book :(.

    I do remember that any logic circuit can be produced by NAND gates no matter wht the logic.

    This particular circuit is very clever with the output feeding back into one of the gates, but 5 gates seems a bit much for a single bit.

    We were taught that memory can be achieved simply by placing a cap behind a diode, but I've never seen it implimented, and I don't know how you would access that memory. You would replace the diode with a transistor to make RAM.