RE: 1-to-2 demux (was: Using large DRAM modules inside the C64)

From: Baltissen, GJPAA (Ruud) (
Date: 2005-10-17 07:24:33

Hallo Magnus,

>  A quad-NAND would do nicely in your case 
>                +------------|-.________
>       ___      |          +-|-'  ROM CS
>   ROM/RAM sel  |          |
>   -------------+-=| )-------|-.________
>   ___________             +-|-'  RAM CS
>   chip select             |
>   ---------------=| )-----+
>                  ^
>                   signal connected to both inputs, so = inverter

I'm sure the above will work perfectly except.... I'll need one IC for every
chipselect ie. four in total. Using OR gates and invertors I need three. And
using 139's I only need two.

> and your mentioning a '139 is just the drugs talking):

No, it isn't.

    / __|__
   / /  |_/     Groetjes, Ruud
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