ULINK: JTAG COMMUNICATION FAILURE
Information in this article applies to:
I have problems when I start debugging using the Keil ULINK
USB-JTAG Adapter. The ULINK driver displays the message:
JTAG Communication Failure
What can cause this error? Is this a problem with the Embedded ICE
of the ARM device?
This message may have several reasons that are listed below:
The Embedded ICE or the JTAG Interface on the ARM device might
The power supply of the ULINK driver might be incorrect. Open
ULINK and set the jumper VCC to 3.3V. For more information
refer to the Getting Started User's Guide, JTAG Debugging -
ULINK: Interface Schematic.
The ARM device may execute some code that interrupts
communication with the Embedded ICE. This happens when the device
executes random code. Some devices have also problems with the JTAG
interface, when the device goes into IDLE mode. To recover such
devices, you may erase the complete program using serial program
Enable the option Project - Options - Debug - ULINK ARM
Debugger Settings - Use Reset at Startup. This ensures that the
ARM device gets a proper reset signal at startup.
When ARM devices work with a slow clock (below 6MHz) the ULINK
may be too fast by default. Reduce the MAX JTAG Clock in the
dialog Project - Options - Debug - ULINK ARM Debugger
For ULINK2 adapters, you may receive this message if you use
the adapter on more than 1 PC and the PC's have different versions
of µVision. New versions of µVision may require an update to the
firmware in the ULINK2 adapter, and older versions may not work
with that update.
Before µVision updates the ULINK2 firmware, it displays a
warning message that allows you to cancel the firmware update. If
you allow the firmware update, remember to update the PC with the
older version so the ULINK2 adapter can be used on both PCs.
- Getting Started User's Guide, JTAG Debugging
The following Discussion Forum threads may
provide information related to this topic.
Last Reviewed: Thursday, April 09, 2009