[Coco] floppy disk controller question for those that still use them

[Darren A]

On 1/27/10, Bob Devries wrote:
> Hi Gene, you said:
>
>> One oddity I tried to check out with
>> a couple of lines of code in my newest joydrv_6551L.sb which tries to read
>> and display in the boot trace, the state of the slot selector in the MPI,
>> which I'd think would be a $33 after a reset.  But its finding a $1D!
>
> Hmm, is the slot selector register readable? The multipak manual says
> nothing about PEEKing the slot register, only POKEing it.
>


Yes it is readable, but only the two lower bits of each nibble are
valid.  You need to AND the value with $33 to mask out the invalid
bits. A value of $1D would then become $13 indicating that SCS is
going to slot 4 and CTS is going to slot 2.

Darren