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How JTAG take control of ARM core?

Note: This was originally posted on 29th July 2010 at http://forums.arm.com

Hello,

I have a question from customer regarding how to disable JTAG in their final product to prevent their application code from explosion from JTAG interface.

Since I am not familiar with JTAG debug module and ARM core interaction mechanism, I would like to know if there is any document talking about the JTAG debug detail procedure.

(1) We have a plan to disable the JTAG port during reset stage of the MCU, and enable it with the built-in ROM code in certain stage. I am not sure if it is workable, any attention needed?

(2) Is the system reset a must when entering JTAG debug mode? If not, please help explain the detail procedure on how JTAG take control of core.

Thanks a lot!

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Joseph Yiu over 12 years ago

Note: This was originally posted on 2nd August 2010 at http://forums.arm.com

Older ARM cores (e.g. ARM7TDMI) has JTAG interface and the descriptions are covered in the
Technical Reference Manuals (TRM). For example, the ARM7TDMI-S TRM can be found in
[url="http://infocenter.arm.com/help/topic/com.arm.doc.ddi0234b/index.html"]http://infocenter.arm.com/help/topic/com.a...234b/index.html[/url]

Newer ARM cores use CoreSight debug architecture.
The document "CoreSight™ Technology System Design Guide" might be useful for you:
[url="http://infocenter.arm.com/help/topic/com.arm.doc.dgi0012d/index.html"]http://infocenter.arm.com/help/topic/com.a...012d/index.html[/url]
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Joseph Yiu over 12 years ago

Note: This was originally posted on 2nd August 2010 at http://forums.arm.com

Older ARM cores (e.g. ARM7TDMI) has JTAG interface and the descriptions are covered in the
Technical Reference Manuals (TRM). For example, the ARM7TDMI-S TRM can be found in
[url="http://infocenter.arm.com/help/topic/com.arm.doc.ddi0234b/index.html"]http://infocenter.arm.com/help/topic/com.a...234b/index.html[/url]

Newer ARM cores use CoreSight debug architecture.
The document "CoreSight™ Technology System Design Guide" might be useful for you:
[url="http://infocenter.arm.com/help/topic/com.arm.doc.dgi0012d/index.html"]http://infocenter.arm.com/help/topic/com.a...012d/index.html[/url]
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