Re: Replacing SRAM with a SIMM
- From: "Kryten" <kryten_droid_obfusticator@xxxxxxxxxxxx>
- Date: Sun, 03 Sep 2006 10:41:55 GMT
"FyberOptic" <fyberoptic@xxxxxxxxx> wrote in message
news:1157220878.647185.241200@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I've got a 6502-based project
So my thought was to take one of these countless 30-pin SIMMs
Good news, there is an easy way to interface DRAM and 6502 chips.
Though you wouldn't think it to look at some of the commercial designs I
have seen, and listen to what most people say.
http://www.howell1964.freeserve.co.uk/projects/DRAM_6502.htm
This circuit supports 16 to 8 address line multiplexing, and 8-bit refresh
address. So a pair of 64Kx4 chips will give you a full memory map.
These days it is cheap and simple to fit a 32K or 128K SRAM chip, so it is
only worth using DRAM for relatively large memories.
Fortunately it is easy to extend the circuit to have more refresh address
bits and multiplex more address lines. The latter can be connected to a
page-select latch.
.
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