ARM Technical Support Knowledge Articles

JTAG RESET LINE FOR CORTEX-M3 DEVICES

Applies to: ULINK USB-JTAG Debugger

Answer


Information in this article applies to:


QUESTION

Is the RESET line in the JTAG interface required for Cortex-M3 Devices?

ANSWER

For a properly integrated Cortex-M3 core, the JTAG RESET line is not necessary since the JTAG software reset command SYSRESETREQ resets the processor core.

But if an application somehow disables the JTAG interface (for example: when the JTAG pins are shared with I/O pins), the debugger cannot connect to the JTAG interface. In such cases a physical chip reset is required to re-establish the JTAG connection to the debugger.

To avoid this, we strongly recommend connecting the RESET line of the microcontroller to the JTAG connector.

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Article last edited on: 2008-09-19 11:01:18

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