22 Mar
2006
22 Mar
'06
9:32 a.m.
The most likely candidate is that you're running afoul of a timing issue.
A good candidate is the reset delay (140 usec minimum). Since TeleDisk
supports 1M/2.88MB data rates as well, it also issues CONFIGURE commands to
the FDC when it changes rate--there might be something there. And a data
rate change is always accompanied by a controller reset--in theory it
doesn't have to be that way, but I found that some controllers gave very
erratic operation if this wasn't done.
While using the 765 data sheet might be good enough for most things, you
should really be using the Intel 82077 as a reference--there are some
differences.
Cheers,
Chuck