Re: 4168 "XRAM" in place of 4364 SRAM

From: silverdr_at_wfmh.org.pl
Date: Sat, 29 Jun 2013 11:44:19 +0200
Message-Id: <0FC1A29F-1F12-4A9D-81F4-FF8CD9321623@wfmh.org.pl>
On 2013-06-29, at 08:38, Ruud@Baltissen.org wrote:

>> Has anyone of you had some experience ....
> 
> Not at all, but I put one of my two brain cells in overgear.

:-D

> If the _RFSH line was meant to be connected to GND or +5V only, the 
> designers could have done it inside the IC. IMHO it is meant to 
> tell the IC it can do a refresh without fear that it will be 
> accessed during that moment.

The datasheet says about three "refresh modes". It also says "The self-refresh mode provides transparent refresh without system overhead". I hoped it to mean that the system doesn't have to do any dynamic stuff around the chip.

> If I was using it in a VIC-20 as RAM 
> expansion, then I would connect it to PHI2, knowing that nothing 
> will access it at the moment PH2 = (L).

Hm.. I should be able to try this easily too. Actually I was thinking of something like that, as PHI2 (HI) is also used for allowing R/_W..

> Question out of curiousity: why using a 4168 and going through that 
> much trouble?

Because I am running out of 6264/4364s, while I have a pile of unused 4168s. If was able to easily make the circuit both SRAM (_RFSH is NC there) and XRAM compatible I'd be happy with this and the chips would find some use ;-)

-- 
SD!
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Received on 2013-06-29 10:00:04

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