17 Dec
2005
17 Dec
'05
3:19 p.m.
BTW it's not complicated at all to support a
secondary FDC (shut down the
primary if it's on the same DMA), the programming is the same.
ImageDisk already has an option to specify the FDC hardware address,
however I do not have a system with two controllers, so I have not gone
any further toward supporting dual FDCs. What do I need to do to "shut
down" the primary FDC - it is just a matter of setting bit 3 in the Digital
output register (See description below).
If this is the case, you could try poking this bit with a debugger, and then
running ImageDisk with an optioh of "IO=372" for the secondary controller
address. If this works, let me know and I'll include an option to disable the
primary controller.
The documents I have describe the "Digital output register"
as:
7 = 0 Reserved
6 = 0 Reserved
5 = 1 Enable drive 1 motor
4 = 1 Enable drive 0 motor
3 = 0 Enable diskette interupts and DMA
2 = 0 Controller reset
1 = 0 Reserved
0 = 0 Select drive 0
1 Select drive 1
From the information you posted, I gather that the
logical extension
to this is:
7 = 1 Enable drive 3 motor
6 = 0 Enable drive 2 motor
5 = 1 Enable drive 1 motor
4 = 1 Enable drive 0 motor
3 = 0 Enable diskette interupts and DMA
2 = 0 Controller reset
1 = 0 Select drive 0-1 11 = Drive 3
1 Select drive 2-3 ie: 10 = Drive 2
0 = 0 Select drive 0-2 01 = Drive 1
1 Select drive 1-3 00 = Drive 0
Is this correct?
Again - I do not have such a controller, so it would be very hard
for me to test and maintain the software - If I make the changes
to support this, are you (or anyone) willing to test it?
Regards,
Dave
--
dave04a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
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