We have a system with a backplane with five slots for ADSP-21065L DSP's based custom cards. Each DSP card has SPORT 0 DR0A and DT0A tied together. TCLK0, RFS0, and the common DT signals are then each run through a 33ohm series to the backplane bus. The problem is that we are having significant noise problems. One slot in our back plane seems to have problems on the TCLK line as the audio crackles until we connect a scope probe to the TCLK line. We have tried various resistor and capacitor combinations which only seem to make the problem worse. We have noted item 21 in the Anomaly list but are not sure how to proceed to fix the problem. Has anyone out there dealt with sport signal termination on the 065L successfully? If so, what was your solution, if you wouldn't mind sharing it. Thanks for your help.
ADSP-21065L SPORT termination problem
Started by ●July 1, 2004
Reply by ●July 1, 20042004-07-01
Steve, Take a look at this application note: "Analog Devices Serial Port Development and Troubleshooting Guide" http://www.analog.com/UploadedFiles/Application_Notes/712188301ee_74.pdf On our system we were not able to eliminate the problems completely by proper termination. We had to include high-current drivers for the long serial lines. HTH, -- Georgi "Steve Holle" <sholle@link-comm.com> wrote in message news:ba83847d.0407010813.bbee8f6@posting.google.com...> We have a system with a backplane with five slots for ADSP-21065L > DSP's based custom cards. Each DSP card has SPORT 0 DR0A and DT0A > tied together. TCLK0, RFS0, and the common DT signals are then each > run through a 33ohm series to the backplane bus. > > The problem is that we are having significant noise problems. One > slot in our back plane seems to have problems on the TCLK line as the > audio crackles until we connect a scope probe to the TCLK line. > > We have tried various resistor and capacitor combinations which only > seem to make the problem worse. We have noted item 21 in the Anomaly > list but are not sure how to proceed to fix the problem. Has anyone > out there dealt with sport signal termination on the 065L > successfully? If so, what was your solution, if you wouldn't mind > sharing it. > > Thanks for your help.
Reply by ●July 2, 20042004-07-02
Our solution required buffers on the TCLK0 and RFS0 signals from the card designated to drive those signals. We use an 74xxx08 because we could get them very small and squeeze them into the design. We are concerned about the DT0A and DR0A signals since they are tied together for multichannel mode and there is no way to buffer them because they need to be bidirectional and there is not direction line. I'm having trouble determining what the load and capacitance limits are for these signals from the data sheet. Anyone know where I can find them? "Georgi Beloev" <gbH8SPAM@beloev.net> wrote in message news:<HaGdnQSKKYikHHndRVn-vA@megapath.net>...> Steve, > > Take a look at this application note: > > "Analog Devices Serial Port Development and Troubleshooting Guide" > http://www.analog.com/UploadedFiles/Application_Notes/712188301ee_74.pdf > > On our system we were not able to eliminate the problems completely by > proper termination. We had to include high-current drivers for the long > serial lines. > > HTH, > -- Georgi > > > > "Steve Holle" <sholle@link-comm.com> wrote in message > news:ba83847d.0407010813.bbee8f6@posting.google.com... > > We have a system with a backplane with five slots for ADSP-21065L > > DSP's based custom cards. Each DSP card has SPORT 0 DR0A and DT0A > > tied together. TCLK0, RFS0, and the common DT signals are then each > > run through a 33ohm series to the backplane bus. > > > > The problem is that we are having significant noise problems. One > > slot in our back plane seems to have problems on the TCLK line as the > > audio crackles until we connect a scope probe to the TCLK line. > > > > We have tried various resistor and capacitor combinations which only > > seem to make the problem worse. We have noted item 21 in the Anomaly > > list but are not sure how to proceed to fix the problem. Has anyone > > out there dealt with sport signal termination on the 065L > > successfully? If so, what was your solution, if you wouldn't mind > > sharing it. > > > > Thanks for your help.
Reply by ●July 6, 20042004-07-06
"Steve Holle" <sholle@link-comm.com> wrote in message news:ba83847d.0407020653.616424a8@posting.google.com...> Our solution required buffers on the TCLK0 and RFS0 signals from the > card designated to drive those signals. We use an 74xxx08 because we > could get them very small and squeeze them into the design. We are > concerned about the DT0A and DR0A signals since they are tied together > for multichannel mode and there is no way to buffer them because they > need to be bidirectional and there is not direction line.I think TFS is used as "Transmit Data Valid" for external logic in multichannel mode. -- Georgi> > I'm having trouble determining what the load and capacitance limits > are for these signals from the data sheet. Anyone know where I can > find them? > > "Georgi Beloev" <gbH8SPAM@beloev.net> wrote in messagenews:<HaGdnQSKKYikHHndRVn-vA@megapath.net>...> > Steve, > > > > Take a look at this application note: > > > > "Analog Devices Serial Port Development and Troubleshooting Guide" > > http://www.analog.com/UploadedFiles/Application_Notes/712188301ee_74.pdf > > > > On our system we were not able to eliminate the problems completely by > > proper termination. We had to include high-current drivers for the long > > serial lines. > > > > HTH, > > -- Georgi > > > > > > > > "Steve Holle" <sholle@link-comm.com> wrote in message > > news:ba83847d.0407010813.bbee8f6@posting.google.com... > > > We have a system with a backplane with five slots for ADSP-21065L > > > DSP's based custom cards. Each DSP card has SPORT 0 DR0A and DT0A > > > tied together. TCLK0, RFS0, and the common DT signals are then each > > > run through a 33ohm series to the backplane bus. > > > > > > The problem is that we are having significant noise problems. One > > > slot in our back plane seems to have problems on the TCLK line as the > > > audio crackles until we connect a scope probe to the TCLK line. > > > > > > We have tried various resistor and capacitor combinations which only > > > seem to make the problem worse. We have noted item 21 in the Anomaly > > > list but are not sure how to proceed to fix the problem. Has anyone > > > out there dealt with sport signal termination on the 065L > > > successfully? If so, what was your solution, if you wouldn't mind > > > sharing it. > > > > > > Thanks for your help.