DMA ISSUE ON H4

[exxos]

You are correct. The Ultra Satan works fine. The Atari test board fails while is passes on every other Atari machine I have. I'm going to complete the second H4 and see what happens there. If the second H4 also fails the DMA test I will look into it.

Maybe the buggy DMA tester is buggy :lol:

[PaulJ]

You are correct. The Ultra Satan works fine. The Atari test board fails while is passes on every other Atari machine I have. I'm going to complete the second H4 and see what happens there. If the second H4 also fails the DMA test I will look into it.

Maybe the buggy DMA tester is buggy :lol:

I doubt it since I've run it on 5 other machines which all pass. What ever it is is minor but it is nice to have something that makes a definitive call. What sucks is there software. Really doesn't tell you what is in error. Very terse error code then tells you to change all the chips. If the second H4 fails I will se if I can determine what it is unhappy with. Would be a nice project to disassemble the test cart code, add some actual definition to failures and transplant some of the tests to diagrom.

[exxos]

@PaulJ Do you have a close up image of the test board showing the chips used on the thing ? Also is it a original kit or a repo ? What DMA chip is being used ?

[PaulJ]

@exxos ,see pic.. It also has circuitry to test parallel interface, and joystick interfaces.

Untitled.jpg

[exxos]

@exxos ,see pic.. It also has circuitry to test parallel interface, and joystick interfaces.

Thanks. Have you put the diag-cart in a DMA loop test and scoped out all the lines on the DMA port ? A1 has caused no end of trouble on STFM's.

[PaulJ]

@exxos , No since the ultra satan was working I didn't devote much time since I wanted to get the H2 #2 working. Plan on getting back to it though since it passes with all the other atari's.

[PaulJ]

@exxos , just ran all the diagcart tests on H4-2 and everything passes except the parallel port. The DMA test passes on this board and I also put in the glitter out of the remake which passes. So I guess there may be some issue with the DMA on the H4-1.

[kodak80]

This is the draft of the patch board.

52C5FD20-E57E-4B8A-8A77-A8B5D8C67CE8.jpeg

C2F206D0-F87D-4B9B-B3A5-9EE8FFA7632B.jpeg

For completeness, this fix is tested and works for me.

[rubber_jonnie]

@exxos Ok, just to ensure I'm understanding the patch board correctly, it fits in the socket for the 74LS245 and inverts the FDCS signal going to pin 19 of the 245? I presume the FDCS signal is taken from the DMA chip directly since the patch board does not allow the original FDCS signal to route from the DMA chip?

I just want to understand before I go and build one of these things.

Ta.

[Icky]

@exxos Ok, just to ensure I'm understanding the patch board correctly, it fits in the socket for the 74LS245 and inverts the FDCS signal going to pin 19 of the 245? I presume the FDCS signal is taken from the DMA chip directly since the patch board does not allow the original FDCS signal to route from the DMA chip?

I just want to understand before I go and build one of these things.

Ta.

Thats correct @rubber_jonnie you can tap FDCS line from pin 19 of the other 74LS245 IC5 above it.