21 Sep
2008
21 Sep
'08
6:02 p.m.
Alexis wrote:
The FDC-1 uses a FD179x controller and it appears it
uses the same
data clock and raw data inputs as the 765.
Not quite. I don't recall the details of the difference, but I think it
may have just been the polarity of one of the signals. The 9229 and
9239 had a configuration input to select between 179x and 765 modes.
The 9216 would directly connect to one, and needed a small amount of
logic (maybe just an inverter) for the other.
The decoder is made up of a 74LS197 (clock divider), a
dual 74LS74 flip-flop,
both used, a 74LS163 counter and an inverter. There are also some open
collector NAND gates to select the clock rate for either 8" or 5.25" drives.
It'll use more individual IC packages, but they're *much* easier to find.
Sure, but it doesn't sound like it's a very good data separator. The
good ones have a PLL (either analog or digital), because it is necessary
to track speed variations, not just of the drive that you're using to
read a disk, but also of the drive that wrote it. Non-PLL data
separators work OK when the disk is both written and read under optimal
conditions, but are unreliable otherwise.
The 9216, 9229 or 9239 are *highly* recommended, as they have a good
digital data separator. The 9229 and 9239 also contain write precomp
logic. The 9239 uses higher resolution timing for its PLL, so it may
perform better.