Analog Devices ADSP-21065L serial port trouble

Hello, all,
I'm having a very strange occurrence with Analog Devices ADSP-21065L
SHARC DSP: the data come out of the serial port with the MSB of each
byte cleared, despite the fact that internally (and I checked this with
the VisualDSP++ debugger) the data have it in both states - sometimes
high, other times low.  This happens only on a handful of boards, and I
don't see any differences in the serial port control registers between
the "good" and the "bad" ones.  As I'm not familiar with hardware (I'm
a firmware engineer, not an electric engineer), I don't know where
exatly to start.  Does anyone have a similar experience?

Any suggestions and opinions are welcome.

Thanks in advance,
    Arkady.

Hi,

Zarin wrote:
> Hello, all,
> I'm having a very strange occurrence with Analog Devices ADSP-21065L
> SHARC DSP: the data come out of the serial port with the MSB of each
> byte cleared, despite the fact that internally (and I checked this with
> the VisualDSP++ debugger) the data have it in both states - sometimes
> high, other times low.  This happens only on a handful of boards, and I
> don't see any differences in the serial port control registers between
> the "good" and the "bad" ones.  As I'm not familiar with hardware (I'm
> a firmware engineer, not an electric engineer), I don't know where
> exatly to start.  Does anyone have a similar experience?
>
> Any suggestions and opinions are welcome.
>
> Thanks in advance,
>     Arkady.

Do all of your boards have the same revision of the DSP chip? Which
one?

JaaC