SPORT problems on 21062

Started by Jason Williams May 19, 2000
Hi all,

I have a custom board with 5 ADSP-21062 processors. 4 of the processors
receive A/D data on their serial ports.

The serial ports are configured for receiving two channels of 32-bit data.
2 of the processors (ID=2 and 4) work fine with no problems. The other two
processors (ID=3 and 5) have a tendency to "slip" the data. What I mean by
that is, the left channel will start out in the left channel and will slide
from the left, through the frame sync, to the right channel and then back
again. Almost like the frame sync is not there (which it is). And this
process does not happen periodically, sometimes it takes a few seconds,
sometimes 10-15 seconds in-between "jumps". All processors are running
essentially the same code, all processors are getting the same clock
signals, there are no reflections or noise in the clock signals.

I am using DMA (with chaining enabled) to read in 512 words at a time. All
the words in the block are skewed by the same amount (I know this because I
have a test pattern going into each channel and can recognize the pattern).
So, this says that the skew is happening whenever the DMA is being
re-initialized. Does the serial port shut down while the DMA chaining is
reloading? If so, why does this work on the other two processors and not
these two? Anybody got any ideas?

Jason Williams
DAC Engineering Team Leader

Digital Audio Corporation
5121 Holly Ridge Dr.
Raleigh, NC 27612