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the number of emu lines of c6671

Hello,

I will use a xds560v2 for three c6671s.

TDO and TDI of JTAG are connected as daisy-chain and the other JTAG signals(TMS, TCK, TRST) and 19 emu lines are connected in parallel to each c6671. I referred to Figure 24. Multiple Device - Parallel Trace Configuration of  document SPRU655I.

According to datasheet, c6671 has 19 emu ports

I am not sure whether all 19 emu ports should be connected or just few emu ports are required.

Should I connect all emu ports?

  • According to document SPRU655I, JTAG signals should not exceed 3 inches in length.

    However, there are different comment on website 'XDS target connection guide' (http://processors.wiki.ti.com/index.php/XDS_Target_Connection_Guide#Multiple_Devices)

    The comment is " In cases where your design has just a few devices (not more than 3) on a serial scan chain and the JTAG signal (TCK, TMS, TDO and TDI) routing is less than 6 inches, buffering the JTAG signals may not be necessary."

    I heard from PCB designer that it is very difficult to route JTAG signals within 3 inches after routing 19 EMU signals within 3 inches. 

    Is there no problem if JTAG signals for three c6671s are routed within 6 inches in length?

  • Hi Yoonsun,

    I have merged your threads. We are working on your thread, we will get back to you.

    Thank you for the post and patience.

  • Hello Kim,

    The requirement of EMU ports depends on the XDS emulator support. Please refer the below section for more details.

    http://processors.wiki.ti.com/index.php/XDS_Target_Connection_Guide#EMU_pin_Considerations

    Regards,
    Senthil

  • Hi Kim,

    As described in the link provided by Senthil, the EMU2-18 signals are only used for the advanced emulation provided by core trace or system trace. These two modes are only supported by a limited number of emulators. If you are not planning on using core trace or system trace than routing the EMU2-18 signals is not necessary. If you are planning on using core trace or system trace, then you should consider whether you need this advanced capability for all three of you SOCs. If you only need the trace capability for one SOC than you can avoid routing the EMU2-18 signals to all three. This is illustrated in figure 23 of spru655i. EMU signals should be routed as high speed signals as described in that document for proper operation. 

    The 3" length of the JTAG signals is needed to achieve the highest speed of JTAG operation. Increasing the length of the JTAG signals to 6" will not cause the interface to fail but will decrease the maximum speed. It is very important that the signal integrity of the JTAG signals be maintained to all the SOCs. This is especially true for the TCK clock signal. Any false edge due to signal reflection will cause the JTAG interface to fail. Based on this it is highly recommended that you buffer the TCK signal when connecting to multiple SOCs. Use a buffer with low skew between the outputs and connect only one SOC to the output of a buffer driver. If your emulator uses RTCK than it should have it's own buffer as well.

    Regards, Bill