20 Jul
2006
20 Jul
'06
4:41 p.m.
Hmm, if I'm thinking right, all I need to do is
invert A7 from the ISA BUS
before it goes through the selection circuitry, and that'll plonk the FDC at a
base address of 0x370 rather than 0x3f0. Does that sound sensible? There's
even an unused NAND gate on the board that I can use to do the inversion if so.
I think that should work...
Yep, that's basically what I did. Of course the ROM firmware won't be any
use any more (I'd pull the ROM just in case it interfers with
something...) but Imagedisk won't care about that.
I can try to find the data sheet on the chip (I know I have it
somewhere), IIRC, theres a pin on the chip that determines the state of
A7 that will select the thing (so it can be put at the primary or
secondary address). I found out about this _after_ adding the inverter...
-tony