28 Nov
2005
28 Nov
'05
7:47 p.m.
On 11/28/2005 at 11:27 AM Dwight K. Elvey wrote:
I don't know of any soft sectored that used
serial
chips. I suspect that it is because these depended
on using illegal data clocking sequences in order
to mark sectors. This would require more external
circuits.
Some of the low end word processors (e.g. Smith Corona) used them (or a
feature of the MPU that simulated a serial chip). No "illegal clocks",
just sync fields embedded in an idle stream. SCM used 5F 5F 5F....16
followed by sector ID information and a CRC. Works just fine. Similarly,
Brother 240K diskettes do not use missing clocks, but rely on illegal GCR
patterns to denote start of sector ID. I believe that the Future Data
systems used a similar scheme for their 8" media. All are soft-sectored.
Cheers,
Chuck