JezC - the second (and laST) H5C1 build

[JezC]

That is just so odd. Your not trying to use the osc and shifter input to the 1772 are you. If you not touched the solder jumper then all is good.

Thought you could try using the osc to rule out clock issues.

Not intentionally...will dig out the H4 to compare signals next.
It's almost a good thing they have what appears to be a similar fault, might mean that a fix on one will also apply to the other one... maybe.

[exxos]

Not intentionally...will dig out the H4 to compare signals next.
It's almost a good thing they have what appears to be a similar fault, might mean that a fix on one will also apply to the other one... maybe.

I looked and the osc is connected by default. You could scope pin 1 of the GAL and see what's there. Maybe try hacking on something like 470R from pin1 to gnd.

The jumper pad connects the clock to the shifter. But you have to remove the OSC for that :(

Having 2 boards with the exact same issue is just weird :(

Might be an idea to post an image of around the GAL /1772 area so we can see how it's setup.

EDIT:
Saying that your other board hasn't got the GAL anyway..

Other than sending me one of those boards to fiddle with, I can't really think of anything else to suggest. :(

[JezC]

Ok, so I managed to sneak a few minutes to try and set up the H4 board to probe the signals around the floppy at boot time...

In true @exxos style, this has itself turned into a bit of a saga :( :roll:

Disconnected the ST536 from it, scavenged the PLCC 68k and PLCC EPROM from one of the H5 boards (plus keyboard & PSU etc)...and it boots to a white screen - argh!
:headbang: :cussing: :stickwhack:

Ok, pull up the jumper cheat sheet viewtopic.php?f=78&t=2785 and re-fit the Glue ROM decode enable jumper...and still a white screen :cry:

Pulled out the PLCC 68k & EPROM, checked the pins & refitted...still no joy.
Attached the 'scope & lots of activity on AS and DTACK, so doing something but no display...

However, it is briefly lighting the Floppy LED so I might be able to get some scope traces of the floppy activity on this early access, so not a great success but maybe not a total washout.

This has of course burned up all the time I could spare (maybe until later tonight), so real progress is minimal so far.

Off to do something hopefully more productive for a few hours.
:sigh:

[JezC]

Found a few minutes to escape to the study & investigate further...the H4 is now booting to the desktop OK!

:yay:

I can even open the contents of the A drive, so all set to scope out the floppy signals on the two boards when I get some more time....

Phew!

[agranlund]

:dualthumbup: :cheers:

[JezC]

:dualthumbup: :cheers:

:thanksblue:

[JezC]

Well, I've started checking a few of the signals (starting at the WD1772) & the H4 (working) and H5C1 (bombs) both seem to show the same signals there (just checking for pulses or steady levels), so I've then looked at the interrupt into the MFP and they look to be pulsing too.
(This is when the system is booting & no floppy in the drive)

I'm not seeing any activity on pin 27 of the 1772 (FDRQ) on either board...but don't know if that means anything (presuming not).

I think I'll have to wire up the logic anaylser and check the whole set of signals in one go...
:sigh:

[JezC]

I set up the logic analyser on the 'scope...only to find that it has "forgotten" that the feature was enabled!
:headbang: :cussing:

So, disconnected that & set up the Saleae instead...first on the working H4 & then moving the clip on the 1772 over to the second H5C1.

I've captured the two waveforms (8 bit data bus, A0,A1, control signals etc.) but there are lots of differences in the traces between the two around where I insert the floppy into the drive while booting (when the FDD LED comes on constantly).

I don't suppose anybody has a picture of what they would expect? Or even to be able to help suggest how to investigate the differences?

I'm off out to do the Dad taxi role in a few minutes but will post some snippets of the two traces later today.

Some data bus pins don't appear to change state on the H5C1 but the DRQ & INTRQ signals look vey different between the boards as well...

Anyway more info later...