[sdiy] SRAM like 5101

[The Old Crow]

On Thu, 11 Apr 2002 jhaible at debitel.net wrote:

> Are there still SRAMs with separate data input and data output pins ?
> The PS-3200 used 5101s (obsolete, and needed several of these because of
> their small memory size).
> 
> I'm looking for something like 512 x 8bit (or slightly larger), separate
> DI and DO pins. I figure this must be a rather big package size (8
> adress pins + 16 data pins alone), so I'm not sure something like that
> even exists. (Maybe they cancelled thar separate DI / DO interface when
> memories got bigger ?)
> 
> Any pointers ?

  SRAM design philosophy went to bidirectional data pins in the late
1970s, mostly due to pin-count reasons as the storage capabilities
increased.  A common 2Kx8 or 8Kx8 CMOS SRAM is recommended today for
retrofitting old memory, with a little extra logic to split the data lines
into inputs and outputs if that is necessary.

  There are dual-ported SRAMs (mostly used for video display cards) which 
have two independent address and data interfaces to the same RAM array.  
The only caveat in using these is that you cannot write a specific 
location on one port while reading that same location on the other port.  
They provide 'busy' signals to help arbitrate such contention.

  Do you have a schematic of the circuit that uses the 5101s?  I'd like to 
see what options can be tried.

Crow
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