[Coco] [Color Computer] Floppy contoler Q

[Robert Gault]

Thanks Art. You are quite correct and I was sloppy.

Arthur Flexser wrote:

> On Sat, 14 Jan 2006, Robert Gault wrote:
> 
> 
>>Bit6 $FF40 is used by Tandy for drive select 3. However, the connection 
>>of this bit to the ribbon cable results in it also being a side select.
>>
>>When single sided drives are used, bit0=drive0, bit1=drive1, 
>>bit2=drive2, and bit6=drive3. With double sided drives and without any 
>>hardware changes to the controller or ribbon cable, bit0=drive0, 
>>bit1=drive1, and bit6= side select.
>>
>>You might think that 3 double sided drives could be used because bit6 
>>could be combined with any of the three bits 0, 1, or 2 resulting in 0, 
>>1, 2, $40, $41, or $42. Unfortunately, the controller does not permit 
>>that because $00 turns off the drives. That leaves you with 1, $41, 2, 
>>and $42 or two double sided drives. You can however, have two double 
>>sided drives and one single sided drive at the same time with the third 
>>drive selected with $40.
>>
> 
> 
> I think you goofed here.  While the bits for DS0, DS1, and DS2 are bits 0, 1,
> and 2, setting each one results in $FF40 values of 1, 2, and 4, so the
> corresponding double sided versions would be $41, $42, and $44.  So, I don't see
> any problem with connecting 3 double-sided drives.
> 
> Art
> 
> 
>