Re: XRAM notes

From: Julian Perry <>
Date: Tue, 11 Mar 2014 12:13:52 +1100
Message-ID: <>
My recollection of XRAM is that it's just self-refreshing/multiplexing DRAM,
designed to be used as a cheap, pin-compatible replacement for SRAM, but needing a
separate clock for refresh, and a longer reset. When I was doing all
the investigation/work on DolphinDOS, I recall seeing a memory
expansion board for the 1541 that had an Xram option on it. It just
needed one additional wire, from memory.
I think it was a variant of the RAMBOarD - - I MIGHT still
have the schematics somewhere - I'll look later.


Tuesday, March 11, 2014, 7:30:51 AM, you wrote:

> When trying to deal with some 4168 XRAM chips, I couldn’t get them
> to work properly. After studying the datasheet I found in the notes:


> Point [2.] seems important to me but I seem to have problems
> interpreting it unambiguously.. or for some other reasons these RAMs still don’t want to work..

> “An initial pause of 2ms is required after power up, followed by
> any 8 _CE cycles and 64 _RFSH cycles before proper device operation
> is achieved. Read, write, and external refresh cycles may be used as
> _CE dummy cycles for initialisation. The 64 refresh dummy cycles can
> be performed before or after the 8 _CE dummy cycles. Both dummy
> cycles must be within AC parameters. See figure 1, below."

> Figure follows as on the picture linked above. How do you
> understand the above? How should it be interpreted? Please note that e. g. here:


> the _RFSH is tied up to VCC..

> --  
> SD!

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Best regards,

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Received on 2014-03-11 02:00:07

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