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Discussing the Open Source FPGA Amiga Project
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 Post subject: Problems...
PostPosted: Sun Apr 15, 2012 9:03 am 
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Joined: Wed Jan 06, 2010 7:47 pm
Posts: 25
Hey all,

two years ago, I built a Minimig and... killed it shortly thereafter by putting it in my hand luggage on a plane. I changed the FPGA and PIC and it did not fix the problem, so I assumed there was physical damage to the PCB. Fast forward to today, I had 10 boards boards made and moved the components over. As it turns out... the PCB wasn't the problem at all. I can't figure out exactly what the problem is.

The PIC bootstraps the FPGA and I am getting video and CPU clocks, but it does not respond to *any* SPI command, so everything past ConfigureFPGA fails and loops forever. My theory is that the 68k is dead and hence the bootloader does not work and boot commands fail. I have ordered some more 68sec000s and some more RAM just in case but is there any way to verify this without writing some my own Verilog code to test the 68k?

Cheers


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 Post subject: Re: Problems...
PostPosted: Sun Apr 15, 2012 10:15 am 
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Joined: Mon Dec 01, 2008 9:58 pm
Posts: 1568
Location: .de
In my experience of several RAM upgrade, if one of the S-RAM chips is damegaed, even the bootloader background color does not appear.
By removing all RAM IC off the board, at least the bootloader background (color 0) should appear. This also is an indicator of a working 68sec000 CPU.

Actually its hard to damage FPGA and CPU.
RAM chips are quite fragile and some even are already dead or partial damaged at arrival.

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 Post subject: Re: Problems...
PostPosted: Sun Apr 15, 2012 11:18 am 
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Joined: Wed Jan 06, 2010 7:47 pm
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Interesting! Off to the lab to try that. On the bright side, RS has RAM stock, ordered 4 chips that I should have tomorrow or the day after. Could find some FPGAs and build someone a Minimig with the other 68ks. Got 9 PCBs left if anyone is interested, otherwise I'll put them on ebay.


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 Post subject: Re: Problems...
PostPosted: Sun Apr 15, 2012 1:03 pm 
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Joined: Wed Jan 06, 2010 7:47 pm
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Hm, when you say that it should change colour, do you mean into bootloader blue? I've removed both chips and the screen just turns on, flickers to black and stays there.

Also, I just probed the FC pins of the 68k and it seems to be changing state on boot, so I think that's probably a good indication that the chip is alive and well.


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 Post subject: Re: Problems...
PostPosted: Sun Apr 15, 2012 3:37 pm 
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Joined: Mon Dec 01, 2008 9:58 pm
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Location: .de
A flickering screen should point out any CPU activity.
I think one of the S-RAM chips is dead and causes bus error, so the system can not work properly.

Some action at the FC (or low adress bus) wire sound good and I think the CPU is still alive.

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 Post subject: Re: Problems...
PostPosted: Mon Apr 16, 2012 1:59 am 
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Joined: Tue Nov 10, 2009 11:56 pm
Posts: 43
Zardoz wrote:
Interesting! Off to the lab to try that. On the bright side, RS has RAM stock, ordered 4 chips that I should have tomorrow or the day after. Could find some FPGAs and build someone a Minimig with the other 68ks. Got 9 PCBs left if anyone is interested, otherwise I'll put them on ebay.


Could you make me one with an 68060? :)


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 Post subject: Re: Problems...
PostPosted: Tue Apr 17, 2012 5:04 pm 
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Works! :-)


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 Post subject: Re: Problems...
PostPosted: Tue Apr 17, 2012 5:06 pm 
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Joined: Mon Dec 01, 2008 9:58 pm
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Location: .de
Great :)

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