4 address lines for 1 bit input

Asked Oct 12 '20 at 22:18

Active Oct 12 '20 at 22:41

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I am currently trying to design a 16 nibble RAM on logisim, whereby it takes 4 data input lines.

However, what I am having the most trouble with is converting the 4 address lines into a single input, such that the RAM circuit should read a 4-bit piece of data as input and set this as the value of the nibble that is defined by the address bits.

For example, if Data = 1000 and Address = 0011, then in the next Clock cycle the value of 4th nibble of the RAM should become 1000, and also this value should be displayed on the output.

I know it involves a multiplexer, but what would act as the 4 selector bits?

edited Oct 12 '20 at 22:41

TonyM

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asked Oct 12 '20 at 22:18

anonymouseeeee

Welcome to the site. The middle section reads like a homework question. Is it? If not, what is it for and why? Background helps a question get a better answer. – TonyM Oct 12 '20 at 22:43
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The address lines are the selector bits – Chris Stratton Oct 12 '20 at 22:44
@TonyM Hello, Yes, it is a circuit homework that involves logisim. – anonymouseeeee Oct 12 '20 at 22:50
Are you building the RAM from individual registers, or are you using the 'RAM' memory device? – Bruce Abbott Oct 12 '20 at 23:41
RAM is addressable, that’s the random feature. in R, if it only had chip select and needed a 1 of 16 Decoder, it wouldn’t be RAM – Tony Stewart EE75 Oct 13 '20 at 02:30
@anonymouseeeee Look up the 7489, 74189, and 74219 devices and read their schematics. I wrote a little something about them [here](https://electronics.stackexchange.com/a/307011/38098), though not a logic analysis of them. Just some history. The schematics on the datasheets will tell you step by step how to make your nibble memory. – jonk Oct 13 '20 at 03:19
@BruceAbbott I am building the RAM from individual registers – anonymouseeeee Oct 13 '20 at 18:32
@TonyStewartSunnyskyguyEE75 Yeah, I figured that out and have now resolved my issue. – anonymouseeeee Oct 13 '20 at 18:33
@jonk Thank you very much for the links. – anonymouseeeee Oct 13 '20 at 18:33

4 address lines for 1 bit input

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