Is it possible to increase a ram ic memory cell count with two of this chip?

For instance, I have two 16x4 ram ic. To increase up to 4-bits to have 16x8, it is straightforward, I just have to connect same address pin of the two chips together.

But how can I have 255x4 with these chips (thanks to the 4 + 4 inputs)?

(Sorry if I am not very clear in my explanations)


1 Answer 1


For 16 by 32 bit word you would need 8 16x4 in parallel, with common address lines. However, whatever is driving the address lines needs to be capable of driving 8 inputs.

For 32x8 then you need to pair up two sets of 16x8 and decode a fifth address line to enable the required pair when appropriate.

For 64x4 then you need to four 16x4s with common address and data lines and decode fifth and sixth address lines to enable the required device when appropriate.

255x4 would mean 16 16x4s and you would need to decode 4 additional address lines. However, that is a lot of small memory chips. You would be better off finding and buying some bigger chips, even if it means not using all the address pins, and tying the remainder to a rail.

  • 1
    \$\begingroup\$ @Ardakaniz try not to use the term memory cells. That term is fairly meaningless in this context. Use the AxD notation instead so we know what you are asking. \$\endgroup\$
    – Trevor_G
    Apr 5, 2017 at 19:59
  • \$\begingroup\$ Ok, I fixed that, as you may have seen, i'm not English, so i may use wrong terms. So, to have 255x4, I must use sixteen 16x4s? I should find another IC which have a directly 255x4, it will be more convenient. \$\endgroup\$
    – Ardakaniz
    Apr 5, 2017 at 20:14
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    \$\begingroup\$ I think everyone meant 256x4 rather than 255x4 but it's still a solid explanation, Trevor and OP. \$\endgroup\$
    – TonyM
    Apr 5, 2017 at 21:16

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