4 Nov
2010
4 Nov
'10
8:06 a.m.
On 11/3/10 11:55 PM, Eric Smith wrote:
This makes it a pain to dump all the bits on a track
at once, when you don't have a priori knowledge of the track format,
because you can't just assert read gate continuously and get good NRZ data from the
drive.
I ran into this about 10 years ago when I was trying to build a circuit to read data from
a Century Data Trident drive.
As Eric said, you can't just assert read gate continuously. At the time, I didn't
have the spec for the Trident interface
(very similar to SMD, it turns out) so I didn't know what the read gate timing was
supposed to look like.
You get very confusing logic analyzer traces if you continuously assert read gate :-(
It looks like there is almost enough circuitry (certainly enough FPGA real estate) in the
disc ferret to run it backwards
as an MFM disk simulator.
I/O pins count may be an issue.