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

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