[Coco] CocoSDC won't stay off

[John Goerzen]

Darren A <mechacoco at ...> writes:

> 
> John, sorry to hear about the probelms you are having. I just tried the
> same steps (64K CoCo 2 with 26-3124 MPI, CoCo SDC in slot 1 and Floppy
> controller in slot 4). DRIVE 0,OFF allowed me to do a DIR on the floppy
> disk. After mounting a DSK image in drive 1 I entered BACKUP 0 TO 1 and it
> copied the entire floppy to the SDC without error.

Hi Darren,

Very nice to hear from you.

I've done some further testing.  I happened across a lot of untested CoCo
parts on eBay the other day, made a low offer which was accepted, and they
arrived yesterday.  Among them was another disk controller (the reason I did
this).  It seems to be working fine, but exhibits exactly the same behavior
as the previous one.

I also tried another test.  Coco SDC and disk controller in MPI in exactly
same configuration as before.

BACKUP 0 TO 1 has the same problem I described.

BACKUP 0 TO 0 works fine!  Prompts me to insert destination disk, writes it
out, perfectly.

> I read some of your previous posts regarding the difficulty you were having
> in getting a floppy controller to work with your CoCo. This leads me to
> believe there may still be some kind of problem with your hardware.
> 
> You also mentioned that the COPY command seems to work with small files but
> not larger ones. This could be an indicator of a problem with the 6809 CPU
> in your CoCo. In particular, the NMI* and HALT* signals are only asserted
> during disk I/O operations. One of these may be failing intermittently and
> be more likely to manifest during a longer I/O operation.

Is it possible this explanation is consistent with BACKUP 0 TO 0 but not
BACKUP 0 TO 1 working?

I should also add that I have done a fairly significant amount of work with
floppies on this machine without issue (other than the earlier intermittent
controller, which now seems resolved).  It included using D19.BIN (that
"Disk Utility") to copy various individual files from old floppies to newer
ones, of varying sizes.  It also included saving programs from tape to disk,
etc.  There were no symptoms like this without the CoCo SDC.

That said, my lot of random CoCo parts includes what appears to be a
modified CoCo 2.  I'll make another post about it.  I don't want to plug any
of my equipment into it until I figure out what the heck it is, though.

Thanks again,

John