PCW expansion RAM decoding?

[erikarn]

hi!

So err, how's the PCW expansion RAM decoding work?

I was looking to build a quick 1MB or 2MB RAM expansion, and from what I understand I should be OK if I decode those four memory range banks into latches and assert MDIS if one of them is set? Does anyone know how quickly I need to assert MDIS so I can supply expansion RAM?

I shouldn't assert it for the lower 512k too, since that'll interfere with the on-board RAM (and the lowest 128k is used for video stuff too.)

Am I missing anything else?

Thanks!


-adrian