Other Parts Discussed in Thread: AMC1303E2520, SN6501, AMC1303M2520
so this is a sort of a continuation of my previous post:
but as I have now discovered that it is probably not the C2000 problem and because I more or less just had a monolog with my self, I'm opening another post here.
So I have a board with multiple SD modulators. I have multiple AMC1303E2520 (Manchester coded internal clock) and 3 AMC1306E25 (Manchester coded external clock, the 3 are clocked together). The AMC1306E25 gave me sporadic erroneous resultants and with some more experimentation I have found that when I'm using AMC1306E25 the sample frequency changes a lot (see my previous post). I had nothing connected to the board just started to test the hardware.
I have now ruled out board layout or the MCU with this text: I have cut the connection to one AMC1303E2520 and patched a neighboring AMC1306E25 into the line that was previously AMC1303E2520. With this now both filters have changing sample frequency. Then I reversed my patch so that the one AMC1303E2520 was patched the lines for AMC1306E25. Now both filters have a stable sample rate.
And this is true for all 3 AMC1306E25. Now the only thing that the AMC1306E25 share is their clock line. I have looked at the clock with a scope (500 MHz scope, short ground clip, 15pF x10 probe) and it is perfect, nice and square, no overshoot, no undershot, no jitter, no missing clock pulses, ... (I have set up a pass fail mask on the scope with tight tolerances - picked up no problems). Then for just good measure I have also AC terminated the clock signals but still I still have the same problems with my changing sample frequency.
The only thing that I can now think off if is somehow I received a whole pack of defective AMC1306E25. I bought them at Mauser, so they should be legit.
Any ideas what I could try? I have tried a lot of stuff in the MCU, but now with this test I think I have ruled out any possibility that MCU has anything to do with my problem.