ULINK: JTAG RESET LINE FOR CORTEX-M3 DEVICES

Information in this article applies to:

• Cortex-M3 Device Debug interface.
• ULINK2 USB-JTAG Adapter.

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.

MORE INFORMATION

• Refer to Start Sequence in the ULINK®2 User's Guide.
• Refer to Debug in the ULINK®2 User's Guide.

Last Reviewed: Friday, September 19, 2008