DMA & FIR Filter, some questions.

Okay, now everything works fine in SOPCBuilder. But I experience a strange behaviour when I'm trying to use the DMA from C-Code through the NIOS Eclipse SBT.

For the hardware design I used the SOPC Builder reference design example which was provided on one of CDs which came with the board (DE2 Dev board). I just disabled and disconnected yet unnecessary devices (e.g. VGA or Audio). I integrated the SGDMA, generated, compiled and loaded the system;

On the software side, I'm using a simple DMA test program, which should 'DMA'-copy an array of 8 'alt_u32'. I appended the source code. The output of my test program is the following.

-- DMA Test --.

Read-address: 8455696

Write-address: 8455736

Preparing memory...

Memory before transfer:

From value 0: 1

From value 1: 4

From value 2: 9

From value 3: 16

From value 4: 25

From value 5: 36

From value 6: 49

From value 7: 64

To value 0: 0

To value 1: 0

To value 2: 0

To value 3: 0

To value 4: 0

To value 5: 0

To value 6: 0

To value 7: 0

Preparing descriptor...

Writing descriptor, Starting DMA...

DMA done...

To value 0: 1

To value 1: 4

To value 2: 9

To value 3: 16

To value 4: 25

To value 5: 0

To value 6: 0

To value 7: 0

Test read, a few seconds later:

To value 0: 1

To value 1: 4

To value 2: 9

To value 3: 16

To value 4: 25

To value 5: 0

To value 6: 0

To value 7: 0

As you see, not all values are getting copied. The values which are copied change, if I change something in the code (uncommenting/commenting some printfs e.g.), but for one 'code-version' stay the same for every program execution. Any idea what causes this behaviour?

Regards,

Sebastian