Re: RAM replacements

Date: Wed, 12 Sep 2012 20:56:16 +0200
Message-ID: <>
Hallo Gerrit,

> The LE-signal for the 74HCT573 is connected to _RAS. The OR-Gate takes 
> _RAS and _CAS as inputs and the output is the _CS signal for the SRAM. 
> In theory, just _CAS should work, but it doesn't, the system crashes, 
> possible due to _CAS being run through the PLA and _RAS going inactive 
> before _CAS does.
> With the OR-Gate the circuit works.

I don't understand this. Using an OR gate means that _CS is only 
active LOW when as well _CAS as _RAS are LOW. Then why doesn't _RAS 
alone work? I cannot image that _RAS starts to early. IMHO it will 
become LOW after every flank of PHI2.

If you has said you ANDed both signals, I would have taken that for 
granted immediately.

   / __|__
  / /  |_/     Groetjes, Ruud Baltissen
  \ \__|_\

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Received on 2012-09-12 19:00:54

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