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DM642 JTAG scan chain

RandyP
Guru* 84110 points

We have a system with 4 x DM642 on a single JTAG scan chain, and cannot get the emulator to connect. We are using a Spectrum Digital XDS560v2,  CCSv5.4, and the latest updated drivers from Check For Updates. We also tried an SD XDS510USB with similar poor results.

The 560v2 reports an IR length of 32 and a DR length of 4. When we try to connect to the first DSP, it fails with error code 1135 the first time, then 1047 when we Retry.

We pulled out an old EVMDM642, and were able to connect easily with either emulator, so the basics of the emulator drivers are fine.

But it is odd that the 560v2 on the EVMDM642 reported an IR length of 38, while the 4 x DM642 reported an IR of 32.

On the scope we can see a delay of 8 TCK's from TDI to TDO on the first DSP, and a delay of 32 TCK's from TDI to TDO at the JTAG header.

What should the IR length be for a single DM642?

Regards,
RandyP

  • 0
    TI__Guru* 84110 points

    After reducing the scan chain down to a single DM642 for debug purposes, we were still unable to make the connection. We checked RESETz, and the DM642 was not being held in reset. Finally, we found a header that needed to be installed to keep from forcing the EMU0/1 pins low.

    So, it turned out that having EMU0/1 low caused the DM642 to go into Boundary Scan mode once the emulator was connected and TCK's were present. This was a board issue in which the JTAG header and the EMU header both needed to be installed; they are not populated in production to save cost and time.

    When the DM642 is in Boundary Scan mode, the IR length is 8 bits. This is why we had the short IR path of 32 for the 4 x DM642. With EMU0/1 at the correct state of 1, the DM642 is in Normal mode and the IR length is 38 for each DM642, or 152 for the entire scan chain.

    The error at connection went away and we were able to successfully connect to all 4 DM642s and inspect/modify internal memory.

    Regards,
    RandyP