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ARM: JTAG problem on developed ARM board

Hi. I designed an ARM7 board with LPC2478 MCU. Unfortunately, JTAG doesn't work like one would expect.

I can download code to FLASH, I can start debugging, BUT every time it comes to the first STR instruction I get "Could not stop device" ERROR. When I don't step the code it goes to some garbage address.

I have ONLY ONE physical pull-up/down resistor on my JTAG 2x10 connector (device is ULINK(non2)).

TCK is pulled to +3.3V with 10k resistor.

Signals DBGEN, TMS, TDI, nTRST, RTCK are terminated inside LPC2478.

I saw on some boards that TCK is pulled down? Is this the source of my problem ?

Ivan

Reply to
Mad I.D.
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Maybe. What other NXP ARM devices have you used? If you've been comfortable with the 21xx-series, and basically imported your initialization steps from working code for those chips, then you may be missing some details that have changed with the 24xx and are not really running with the clock speed you think you're running at. That can throw off the JTAG link and lead to unexpected behavior.

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Rich Webb     Norfolk, VA
Reply to
Rich Webb

You probably need more resistors on the JTAG interface - see the ARM documentation.

Leon

Reply to
Leon

Sorry, it has internal pull-ups as you mentioned.

Leon

Reply to
Leon

IIRC, the JTAG lines should be all pulled up with suitable resistors.

Are you sure that there is not an undesired connection from WR- to some weird place on the board?

Did you configure the debugger for ARM7TDMI-S?

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Tauno Voipio
tauno voipio (at) iki fi
Reply to
Tauno Voipio

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