On Sunday (09/08/2013 at 03:33PM -0700), Chuck Guzis wrote:
On 09/08/2013 11:34 AM, Tony Duell wrote:
So if the sector pulse is a few bit-times off, it
doesn't matter. The
controlelr will not see the 'right' number of 0's, but it doesn't count
them anyeway. I'll recgnise the '1' and start reading the header as normal.
Anent that, I once did a project that attempted to synthesize sector
pulses using soft-sector 5.25" media on old belt-driven drives
(e.g. Shugart SA400) that used very primitive speed controls. Since
you had only the index pulse to sync an entire rotation from, the
speed variations (particularly ISV) were entirely too large to do
this reliably. Direct-drive floppies (e.g. Teac FD55) were
considerably better, but a random sampling of various brands of
5.25" media pointed up reliability to be less than ideal.
Yup. But 3.5" drives and media are plenty stable and so my emulator
uses those and every email I get asking if someone can use the board
with a 5.25" drive gets a reply they weren't hoping for :-(
I can understand wanting to make something "period correct" for sure.
But I went for small size and ease of reproducability by multiple
different skill sets. My board has two DIPs on it and the code is maybe
100 lines of C on an ATMEL AVR. It installs between the drives and the
controller-- as a "bump" in the ribbon cable and it supports emulation
of two drives at the same time. I would think a similar approach could
be used for RK05... or, of course, you could build it inside the drive
or onto the controller itself.
Chris
--
Chris Elmquist