ARM Technical Support Knowledge Articles

Do I need to connect DBGRQ and DBGACK to the 20-pin JTAG connector?

Applies to: DSTREAM, RealView ICE and Trace (RVI / RVT)

Answer

The DBGRQ and DBGACK pins of the 20-pin JTAG connector are not used by ARM's debug tools. Instead, the tools access those signals inside of the core via JTAG.

Within both the DSTREAM and RealView ICE (RVI) units, these signals are connected to an internal FPGA, but this functionality is not implemented in the firmware or in the RVD or DS-5 debuggers.

DBGRQ and DBGACK were added to the 20-way JTAG connector specification so that they could be used by third-party JTAG tools.

When using ARM brand debug tools, you do not need to route DBGRQ and DBGACK to pins of the ASIC. Instead you can just pull DBGRQ low inside of the ASIC and DBGACK high or low at the JTAG connector.

Article last edited on: 2011-11-04 14:30:21

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