On Tue, 2 Mar 1999, Hans Korving wrote:
> Is it possible to make the MegaRAM yourself using all new parts?
> Or do you need old cartridges?
> Anybody has any schematics?
It's perfectly possible. You can use the same memory IC's used in Memory
Mapper. The difference is only the block switching circuit.
I don't know anybody who has the schematics, but it's not very difficult
to create one. The special feature is the port 8Eh, that selects between
BLOCK SELECT mode and WRITE ENABLE mode.
In a Megaram, when you execute a "IN A,(8Eh)", you put Megaram in WRITE
ENABLE MODE. The accumulator receives garbage. When you execute a
"OUT (8Eh),A", you put Megaram in BLOCK SELECT MODE (exactly as a Megarom
cartridge), whatever the contents in the accumulator.
In Brazil, we have Megaram models of 256kb, 512kb and 768kb.
Greetins from Brazil!
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Marco Antonio Simon Dal Poz http://www.lsi.usp.br/~mdalpoz
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