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Yes a typo in my diagram pin 5 should be drive 0 - I did create it in the early hours - thought I had found all the bugs.
Yes a typo in my diagram pin 5 should be drive 0 - I did create it in the early hours - thought I had found all the bugs.
12 pins better than me though ;)
I was just scoping the RDY line on the DMA and noticed the undershoot like in your BAD DMA MYTH http://www.exxosforum.co.uk/atari/last/DMAfix/.exxos wrote: 08 Oct 2018 22:03 Just looking through the DMA pdf...
It only seems to say is driven with a open collector, but does not really say is needed for any reason..
It can also be where you have grounded the scope.. assuming you are on a gnd point very close to the DMA..Icky wrote: 08 Oct 2018 22:23 I was just scoping the RDY line on the DMA and noticed the undershoot like in your BAD DMA MYTH http://www.exxosforum.co.uk/atari/last/DMAfix/.
Probe is on 10x and ground point I am currently using is the DMA socket shield lugs. Will move it closer and look at the other lines.exxos wrote: 08 Oct 2018 22:26It can also be where you have grounded the scope.. assuming you are on a gnd point very close to the DMA..Icky wrote: 08 Oct 2018 22:23 I was just scoping the RDY line on the DMA and noticed the undershoot like in your BAD DMA MYTH http://www.exxosforum.co.uk/atari/last/DMAfix/.
Also try on x10 probe... Sometimes a probe itself can appear to give you things which are not actually there...
It is also worth probing every pin of the DMA to see if anything looks odd... The address and databus to the DMA will likely look like chaos anyway..
So far nothing looks out of place. Have even tried different ACSI cables and drives.Icky wrote: 08 Oct 2018 22:31Probe is on 10x and ground point I am currently using is the DMA socket shield lugs. Will move it closer and look at the other lines.exxos wrote: 08 Oct 2018 22:26
It can also be where you have grounded the scope.. assuming you are on a gnd point very close to the DMA..
Also try on x10 probe... Sometimes a probe itself can appear to give you things which are not actually there...
It is also worth probing every pin of the DMA to see if anything looks odd... The address and databus to the DMA will likely look like chaos anyway..
Have you tried with and without the RP900 in place ?Icky wrote: 08 Oct 2018 23:38 Odd though as I did get the device recognised once but not since - must of been a fluke or all the stars aligned
Just did - no difference still doesn't see floppy when hdd is connected
Nope don't have a -001 DMA just -38'sexxos wrote: 08 Oct 2018 23:51 Other than that TTL chip there isn't much else to check... for the hell of it, if you have a 001 DMA :lol: