ULINK: PHILIPS LPC2000 ARM DEVICE DOES NOT REACT

Information in this article applies to:

• ULINK USB-JTAG Adapter
• ULINK2 USB-JTAG Adapter

QUESTION

I have worked several days successfully with the Keil ULINK and a Philips/NXP LPC2000 ARM device. Now, when I download a slightly modified application the device no longer responds.

I only get an error message box with:

JTAG Communication Error

What can cause this?

ANSWER

Your application program has most likely disabled the JTAG port during program execution. ARM devices start program execution even when the JTAG adapter is connected. When your application software disables the JTAG port, it is no longer possible to connect to the device via the JTAG interface.

You may recover an NXP LPC2000 ARM device with the Flash Magic Programming Tool from Embedded Systems Academy that erases the application software via a serial interface.

Once you have recovered your device, you should use a while loop at the main entry of your application program as described under ULINK: RESET BEHAVIOUR ON PHILIPS LPC2000 DEVICES. This technique allows you to analyze the instruction (typically in the device initialization) that disables the JTAG interface.

For example, the execution of the following C statement disables the JTAG pins:

PINSEL2 = 0x8

Altering PINSEL2 in this way, basically disables the JTAG port.

Other reasons for such a problem might be the Watchdog timer. When you enable the watchdog, debugging may fail. So you should search your program for sequences like the following:

WDTC = 15103; // Timer reload value 15103*4*(1/60MHz)=1.0ms
WDMOD = 3;    // WDEN = WDRESET = 1

Basically, the watchdog should be not enabled under debugging.

MORE INFORMATION

• Refer to Downloading with Flash Magic in the MCB2100 User's Guide.
• Refer to Downloading with Flash Magic in the MCB2103 User's Guide.
• Refer to Downloading with Flash Magic in the MCB2130 User's Guide.
• Refer to Downloading with Flash Magic in the MCB2140 User's Guide.
• Refer to Downloading with Flash Magic in the MCB2300 User's Guide.

SEE ALSO

• ULINK: RESET BEHAVIOUR ON PHILIPS LPC2000 DEVICES
• ULINK: JTAG COMMUNICATION FAILURE
• ULINK: LPC2000 SINGLE STEP AT RESET APPEARS TO FAIL
• ULINK: RECOVER STR71X WHEN JTAG DISABLE
• ULINK: ATMEL AT91SAM7 DEVICE DOES NOT REACT

FORUM THREADS

The following Discussion Forum threads may provide information related to this topic.

• JTAG Device chain error
• JTAG Communication Failure / With ISP no erase of flash possible
• JTAG communication failour
• JTAG Communication failure
• Could not stop ARM device?
• ULINK - CANNOT STOP ARM DEVICE!
• UART0 and LPC2148
• No JTAG device found
• ULINK JTAG communication Failure? HELP!
• Ulink problem?

Last Reviewed: Thursday, February 28, 2008