For a home project I am attempting to debug a VoIP phone. It has 2 ASICs that appear custom. One definitely has an ARM11 core (The firmware includes 3 files, 2 look encrypted the 3rd is ARM code that seems to cover all features). The board has 20 pads on it which allowed easy attachment of a JTAG header. But when I connect to it with any of the Jlink tools they all fail silently. The only tool that gives me any feedback is Jlink.exe and it says "Could not measure total IR len. TDO is constant high." Just to make sure I wasn't crazy I brought it to work and used a Jlink there, but got the same results. Tear down of the hardware
I tested it with a multimeter and TDO and its ground are both high. What does that mean?
Does that mean JTAG has been disabled in the code, or in hardware? If code, is there a specific address in the code typically associated with disabling JTAG?
I tested it with a multimeter and TDO and its ground are both high. What does that mean?
Does that mean JTAG has been disabled in the code, or in hardware? If code, is there a specific address in the code typically associated with disabling JTAG?