ARM Technical Support Knowledge Articles

Why does GDB show "Device is not selected" if UNKNOWN or non-ARM devices are present in the scanchain?

Applies to: RealView Development Suite (RVDS), RealView ICE and Trace (RVI / RVT)


The standalone RealView ICE (RVI) product install (v3.1 and later) includes Eclipse with GDB-RVI debug support. This allows basic debug of ARM targets using the free Eclipse frontend without the need for an additional debugger like RealView Debugger (RVD).

GDB-RVI support currently has a limitation which prevents target configurations including non-ARM devices from working (e.g. DSPs)

After using the RealView ICE Configuration (RVConfig) utility to describe your targets scanchain, the following error is displayed in Eclipse: "Device is not selected"

The workaround is to manually replace all the non-ARM devices in the JTAG chain with ARM devices of equivalent instruction register (IR) lengths. Note that the IR length and the device position must be identical to the original layout. This ensures the JTAG chain specified matches the hardware.

For example: If your JTAG chain has a custom JTAG device with an IR length of 5 bits you can replace this device with any ARM11xx device as they also use an IR of 5 bits wide. In the case of a device with an IR length of 4 bits you can use an ARM9xx device. 

This solution will only work with custom JTAG devices for which matching ARM devices exist.

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