Reading TRS-80 discs (was RE: Archiving old discs...)

From: allisonp_at_world.std.com <(allisonp_at_world.std.com)>
Date: Tue Sep 14 16:05:17 1999

> seemed to be little or no extra circuitry required for FM. Is that
> correct?

SMC926x, 37c65 and later all support fm and MFM regardless of board design
ans the general design uses that... HOWEVER... if you use a 37c65 let's
say with a 8mhz crystal instead of the expected 16mhz you may not be able
to do the higher data rates for example. Also if you do not supply the
9.6mhz clock then 1.2mb can be done.
 
> A question for Allison:
> Which, if any, of the chips will do FM regardless of the board design and
> implementation? Or is it ALWAYS an issue of board rather than chip?

1771 though it's poor and the clock must be correct for the size drive.
It's poor as it's internal data seperator is junk. The external data sep
will be board specific.

37c65 and 37c66x are all fully contained but you MUST supply the correct
clocks and program them correctly. There are plenty of others in that
group. Some of the WD17xx parts will also but again there are some design
considerations for them like the 1770 will not do the rates required for
8" drives (slow mos).

I have a 765 design that does all rates and formats using the 9229 clock
data sep chip or also a gate array part designed for the task.



Allison
Received on Tue Sep 14 1999 - 16:05:17 BST