ARM Technical Support Knowledge Articles

Multi-ICE cannot connect to a core with a slow clock / Multi-ICE cannot connect to an AT91 board / Can I stop the core clock when debugging with Multi-ICE?

Applies to: Multi-ICE

Answer

When trying to connect Multi-ICE to a target running at less than 100KHz, it usually reports a timeout error: "Target processor would not enter debug state when requested." For instance, this is the case of Atmel AT91 processors, which run at 32KHz after reset.

These timeout errors are reported when the core takes a long time to finish the actions initiated by Multi-ICE, such as enter debug state or access the memory system.

The time it takes the core to perform the action is proportional to the core clock period and the Multi-ICE timeout is proportional to the JTAG clock period. Therefore, in order to connect to slow targets you should not work at the default 10MHz JTAG clock, but should slow down the JTAG clock accordingly. To do this you can:

  • Use adaptive clocking, if the target allows it.
     
  • Set the JTAG clock frequency manually in Multi-ICE Server => Settings => JTAG Settings. In order to connect to a target running at 32KHz you should set TCK at 8KHz or less.
     
  • Increase the clock speed of your target, so you can connect with Multi-ICE at the default 10MHz. If the clock speed is configurable, the code that increases the clock speed should be included in the boot ROM, so it will usually be executed before connecting with Multi-ICE.

When working with very slow targets (clock running at several Hz or stopped for several seconds), Multi-ICE will fail. This is sometimes the case when working with hardware emulators. In this case we recommend that you use RealView ICE instead, which provides better support for this kind of targets.

Article last edited on: 2008-09-09 15:47:39

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