Question to the tech guys

[A6000]

hello all,

I am not a qualified tech guy but from memory the fc pins selected 1 of 5 address spaces, user code, user data, supervisor code, supervisor data and interrupt acknowledge.

I don't know what gayle does, but it probably decodes the interrupt acknowledge signal, also the fc lines are required by the 68881/68882 FPU.

[A6000]

I think that all memory in the amiga is user space and that supervisor space is not used at all, although I would be interested to learn where it is documented that custom chip registers use supervisor data space.

BBOAH tells me that gayle implements the IDE interface which must use an interrupt or several, it is possible that gayle could have registers in supervisor space.

I have now dug up a data sheet and checked the truth table of the FC outputs, with only two outputs being decoded, if  the two lines are FC2 and FC0, then interrupt acknowledge, user data space and supervisor data space can be decoded.

Sorry if this post seems a little unplanned, it has been edited and added to, several times since I originally posted it.