???! The value for R must be a valid sector number.
For floppies
that is never zero.
There are a lot of floppies with sector numbers starting with
0.
765 can read them and write them.
Maybe... there are caveats on that. Technically a sector number of 0
should not be used.
Did a lot of work at "NEC" (US arm then was NEC Micromputers USA, then later
NEC Electronics USA.) in the early years when they were developing and
marketing that and a HDC. I was on the hardware/technical side.
When I designed the 765 based disk system in my D6809/CUBIX system, I "didn't
know better" and numbered the sectors within a track from zero - this would
have been early to mid 80's.
Never changed it, as it has never caused a problem - versions of this system
were built with both NEC and Intel (8272) controllers, and used for many years.
ImageDisk reads and recreates CUBIX disks with no problems.
I cannot find any information in the NEC data sheet which describes any
restriction on the sector number (other than that it is one byte) - can you
provide a reference to these caveats? this is the first I've heard of them.
Regards,
Dave
--
dave04a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools:
www.dunfield.com
com Collector of vintage computing equipment:
http://www.parse.com/~ddunfield/museum/index.html
