amiga floppy disk reading experience

[Eric Smith]

Chuck Guzis wrote:
> Take a look at some of the old Western Digitial FDC app notes,
> particularly those for the 179x controllers for ideas on how data
> separators can be implemented.
>    
Note that the only data separator worth a damn in the WDC app note are 
the two that use PLLs.  The most commonly used was the one in Figure 14 
that uses a 74LS629 VCO and the phase comparator of the WD1691.  The 
circuit by MPI in Figure 13 that uses an MC4024 VCO looks OK but I 
haven't seen it used.  The rest are crap.

Figure 11 uses a one-shot, and won't work reliably even for single 
density.  It's comparable to the worthless data separator built into the 
1771.  Figure 12 uses a state machine and works approximately the same 
way the Apple II read state machine works.  It's probably good enough 
for single density, but won't work reliably for double density.

Eric