Forums

SPORT Multichannel Mode

Started by Steve Holle August 20, 2003
We are using ADSP-21065L SHARC DSPs and would like to tie up to 24 of
them together using the SPORT in Multichannel mode.  As we understand
it, we need to tie the RXD and TXD signals together on all DSPs.  Then
we need to tie the DSP set up as the master RFS, TCLK, and RCLK
signals to the corresponding signals on all the other slave DSP's,
programming them for individual TX and RX time slots :

MASTER     SLAVE             SLAVE

RXD---|	RXD---|		RXD---|
      |<-------->|<--- ...-------->|
TXD---|	TXD---|		TXD---|

           RFS               RFS
RFS---------^--------- ...----^

           TCLK              TCLK
TCLK--------^--------- ...----^

           RCLK              RCLK
RCLK--------^--------- ...----^


Is this the correct connection method?  
What is the longest recommended distance for the signals?
Are there any "gotchas" I need to look out for?

Thanks for your help.
We are using ADSP-21065L SHARC DSPs and would like to tie up to 24 of
them together using the SPORT in Multichannel mode.  As we understand
it, we need to tie the RXD and TXD signals together on all DSPs.  Then
we need to tie the DSP set up as the master RFS, TCLK, and RCLK
signals to the corresponding signals on all the other slave DSP's,
programming them for individual TX and RX time slots :

MASTER     SLAVE             SLAVE

RXD---|	RXD---|		RXD---|
      |<-------->|<--- ...-------->|
TXD---|	TXD---|		TXD---|

           RFS               RFS
RFS---------^--------- ...----^

           TCLK              TCLK
TCLK--------^--------- ...----^

           RCLK              RCLK
RCLK--------^--------- ...----^


Is this the correct connection method?  
What is the longest recommended distance for the signals?
Are there any "gotchas" I need to look out for?

Thanks for your help.
Mike Rosing <rosing@neurophys.wisc.edu> wrote in news:3F431238.6070303
@neurophys.wisc.edu:

> Steve Holle wrote: >> We are using ADSP-21065L SHARC DSPs and would like to tie up to 24 of >> them together using the SPORT in Multichannel mode. As we understand >> it, we need to tie the RXD and TXD signals together on all DSPs. Then >> we need to tie the DSP set up as the master RFS, TCLK, and RCLK >> signals to the corresponding signals on all the other slave DSP's, >> programming them for individual TX and RX time slots : >> >> MASTER SLAVE SLAVE >> >> RXD---| RXD---| RXD---| >> |<-------->|<--- ...-------->| >> TXD---| TXD---| TXD---| >> >> RFS RFS >> RFS---------^--------- ...----^ >> >> TCLK TCLK >> TCLK--------^--------- ...----^ >> >> RCLK RCLK >> RCLK--------^--------- ...----^ >> >> >> Is this the correct connection method? >> What is the longest recommended distance for the signals? >> Are there any "gotchas" I need to look out for? > > I've never done this, so ignoring me is probably safe :-) > but I'd think you want to send the TXD of the master to the RXD > of the slaves. I think wave form is more important that distance, > so board layout and cabling may help as will some buffering. I'm > not sure what the timing problems might be, if it's supposed to be > 2 way, then having each slave fill the correct time slot on the > receive seems very difficult. > > Patience, persistence, truth, > Dr. mike >
Do you want the master DSP to talk to all the slaves and the slaves to talk to only the master? In this case Mike's idea is basically correct in that you want the DT line from the master DSP to connect to the DR lines of the slaves and the converse. The TCLK line is configured as an input on all devices and is connected to RCLK. RCLK is an input on the slaves and driven by the master. I wouldn't connect all of the SHARCs together without buffers. The TFS line is used as a transmit enable line in multichannel mode. You can build a more flexible interface by using a multiport arrangement using 485 or LVDS transceivers. We are using the new ADSP-21262 SHARC for this type of interface. We just announced our new dspstak 21262 board based on the ADSP-21262. We also have ADSP-21161 based products. I would use either of these DSPs instead of the ADSP-21065L. You might take a look at these boards on our web site. -- Al Clark Danville Signal Processing, Inc. -------------------------------------------------------------------- Purveyors of Fine DSP Hardware and other Cool Stuff Available at http://www.danvillesignal.com
Al Clark <dsp@danvillesignal.com> wrote in message news:<Xns93DE93C0644AAaclarkdanvillesignal@66.133.130.30>...
> Mike Rosing <rosing@neurophys.wisc.edu> wrote in news:3F431238.6070303 > @neurophys.wisc.edu: > > > Steve Holle wrote: > >> We are using ADSP-21065L SHARC DSPs and would like to tie up to 24 of > >> them together using the SPORT in Multichannel mode. As we understand > >> it, we need to tie the RXD and TXD signals together on all DSPs. Then > >> we need to tie the DSP set up as the master RFS, TCLK, and RCLK > >> signals to the corresponding signals on all the other slave DSP's, > >> programming them for individual TX and RX time slots : > >> > >> MASTER SLAVE SLAVE > >> > >> RXD---| RXD---| RXD---| > >> |<-------->|<--- ...-------->| > >> TXD---| TXD---| TXD---| > >> > >> RFS RFS > >> RFS---------^--------- ...----^ > >> > >> TCLK TCLK > >> TCLK--------^--------- ...----^ > >> > >> RCLK RCLK > >> RCLK--------^--------- ...----^ > >> > >> > >> Is this the correct connection method? > >> What is the longest recommended distance for the signals? > >> Are there any "gotchas" I need to look out for? > > > > I've never done this, so ignoring me is probably safe :-) > > but I'd think you want to send the TXD of the master to the RXD > > of the slaves. I think wave form is more important that distance, > > so board layout and cabling may help as will some buffering. I'm > > not sure what the timing problems might be, if it's supposed to be > > 2 way, then having each slave fill the correct time slot on the > > receive seems very difficult. > > > > Patience, persistence, truth, > > Dr. mike > > > > Do you want the master DSP to talk to all the slaves and the slaves to > talk to only the master? > > In this case Mike's idea is basically correct in that you want the DT > line from the master DSP to connect to the DR lines of the slaves and the > converse. > > The TCLK line is configured as an input on all devices and is connected > to RCLK. RCLK is an input on the slaves and driven by the master. > > I wouldn't connect all of the SHARCs together without buffers. The TFS > line is used as a transmit enable line in multichannel mode. > > You can build a more flexible interface by using a multiport arrangement > using 485 or LVDS transceivers. We are using the new ADSP-21262 SHARC for > this type of interface. > > We just announced our new dspstak 21262 board based on the ADSP-21262. We > also have ADSP-21161 based products. I would use either of these DSPs > instead of the ADSP-21065L. You might take a look at these boards on our > web site.
I'm really looking for a TDM system with each connected DSP providing two, 16-bit samples in a time slot different for each processor. In a practical sense, the master is no different than any of the slaves except the master generates the sync and clock signals. There would not be many receivers and one transmitter but all would transmit during the assigned time slot and receive all, including their own data although that would be somewhat redundant.
sholle@link-comm.com (Steve Holle) wrote in
news:ba83847d.0308220712.8d3a067@posting.google.com: 

> Al Clark <dsp@danvillesignal.com> wrote in message > news:<Xns93DE93C0644AAaclarkdanvillesignal@66.133.130.30>... >> Mike Rosing <rosing@neurophys.wisc.edu> wrote in >> news:3F431238.6070303 @neurophys.wisc.edu: >> >> > Steve Holle wrote: >> >> We are using ADSP-21065L SHARC DSPs and would like to tie up to 24 >> >> of them together using the SPORT in Multichannel mode. As we >> >> understand it, we need to tie the RXD and TXD signals together on >> >> all DSPs. Then we need to tie the DSP set up as the master RFS, >> >> TCLK, and RCLK signals to the corresponding signals on all the >> >> other slave DSP's, programming them for individual TX and RX time >> >> slots : >> >> >> >> MASTER SLAVE SLAVE >> >> >> >> RXD---| RXD---| RXD---| >> >> |<-------->|<--- ...-------->| >> >> TXD---| TXD---| TXD---| >> >> >> >> RFS RFS >> >> RFS---------^--------- ...----^ >> >> >> >> TCLK TCLK >> >> TCLK--------^--------- ...----^ >> >> >> >> RCLK RCLK >> >> RCLK--------^--------- ...----^ >> >> >> >> >> >> Is this the correct connection method? >> >> What is the longest recommended distance for the signals? >> >> Are there any "gotchas" I need to look out for? >> > >> > I've never done this, so ignoring me is probably safe :-) >> > but I'd think you want to send the TXD of the master to the RXD >> > of the slaves. I think wave form is more important that distance, >> > so board layout and cabling may help as will some buffering. I'm >> > not sure what the timing problems might be, if it's supposed to be >> > 2 way, then having each slave fill the correct time slot on the >> > receive seems very difficult. >> > >> > Patience, persistence, truth, >> > Dr. mike >> > >> >> Do you want the master DSP to talk to all the slaves and the slaves >> to talk to only the master? >> >> In this case Mike's idea is basically correct in that you want the DT >> line from the master DSP to connect to the DR lines of the slaves and >> the converse. >> >> The TCLK line is configured as an input on all devices and is >> connected to RCLK. RCLK is an input on the slaves and driven by the >> master. >> >> I wouldn't connect all of the SHARCs together without buffers. The >> TFS line is used as a transmit enable line in multichannel mode. >> >> You can build a more flexible interface by using a multiport >> arrangement using 485 or LVDS transceivers. We are using the new >> ADSP-21262 SHARC for this type of interface. >> >> We just announced our new dspstak 21262 board based on the >> ADSP-21262. We also have ADSP-21161 based products. I would use >> either of these DSPs instead of the ADSP-21065L. You might take a >> look at these boards on our web site. > I'm really looking for a TDM system with each connected DSP providing > two, 16-bit samples in a time slot different for each processor. In a > practical sense, the master is no different than any of the slaves > except the master generates the sync and clock signals. There would > not be many receivers and one transmitter but all would transmit > during the assigned time slot and receive all, including their own > data although that would be somewhat redundant. >
In this case you need to create a multiport bus using the RS-485 or LVDS style transceivers. This is the same basic interface that we are implementing in one of our designs. If your sample rate is very high, use LVDS not RS-485. -- Al Clark Danville Signal Processing, Inc. -------------------------------------------------------------------- Purveyors of Fine DSP Hardware and other Cool Stuff Available at http://www.danvillesignal.com