General procedure

If you experience problems with a J-Link / J-Trace, you should follow the steps below to solve these problems:

1. Close all running applications on your host system.
2. Disconnect the J-Link / J-Trace device from USB.
3. Power-off target.
4. Re-connect J-Link / J-Trace with host system (attach USB cable).
5. Power-on target.
6. Try your target application again. If the problem vanished, you are done; other- wise continue.
7. Close all running applications on your host system again.
8. Disconnect the J-Link / J-Trace device from USB.
9. Power-off target.
10. Re-connect J-Link / J-Trace with host system (attach USB cable).
11. Power-on target.
12. Start JLink.exe.
13. If JLink.exe reports the J-Link / J-Trace serial number and the target processor™s core ID, the J-Link / J-Trace is working properly and cannot be the cause of your problem.
14. If JLink.exe is unable to read the target processor™s core ID you should analyze the communication between your target and J-Link / J-Trace with a logic analyzer or oscilloscope.
15. If your problem persists and you own an original product (not an OEM version), see section "Contacting support" .

Typical problem scenarios

J-Link / J-Trace LED is off
Meaning:
The USB connection does not work.
Remedy:
Check the USB connection. Try to re-initialize J-Link / J-Trace by disconnecting and reconnecting it. Make sure that the connectors are firmly attached. Check the cable connections on your J-Link / J-Trace and the computer. If this does not solve the problem, check if your cable is defective. If the USB cable is ok, try a different host computer.

J-Link / J-Trace LED is flashing at a high frequency
Meaning:
J-Link / J-Trace could not be enumerated by the USB controller.
Most likely reasons:
a.) Another program is already using J-Link / J-Trace.
b.) The J-Link USB driver does not work correctly.
Remedy:
a.) Close all running applications and try to reinitialize J-Link / J-Trace by disconnecting and reconnecting it.
b.) If the LED blinks permanently, check the correct installation of the J-Link USB driver. Deinstall and reinstall the driver

J-Link/J-Trace does not get any connection to the target
Most likely reasons:
a.) The JTAG cable is defective.
b.) The target hardware is defective
Remedy:
Follow the steps as described in the section "General procedure"

Signal analysis

This is the signal sequence output by J-Link / J-Trace at start of JLink.exe. It should be used as reference when tracing potential J-Link / J-Trace related hardware problems.

The sequence consists of the following sections:

• 5 clocks: TDI low, TMS high. Brings TAP controller into RESET state
• 1 clock: TDI low, TMS low: Brings TAP controller into IDLE state
• 2 clocks: TDI low, TMS high: Brings TAP controller into IR-SCAN state
• 2 clocks: TDI low, TMS low: Brings TAP controller into SHIFT-IR state
• 32 clocks: TMS low, TDI: 0x05253000 (lsb first): J-Link Signature as IR data
• 240 clocks: TMS low, last clock high, TDI high: Bypass command
• 1 clock: TDI low, TMS high: Brings TAP controller into UPDATE-IR state.

J-Link / J-Trace checks the output of the device (output on TDO) for the signature to measure the IR length. For ARM7 / ARM9 chips, the IR length is 4, which means TDO shifts out the data shifted in on TDI with 4 clock cycles delay. If you compare the screen shot with your own measurements, the signals of TCK, TMS, TDI, and TDO should be identical. Note that the TDO signal is undefined for the first 10 clocks, since the output is usually tristated and the signal level depends on external components connected to TDO, such as pull-up or pull-down.

Zoom-inThe next screenshot shows the first 6 clock cycles of the screenshot above. For the first 5 clock cycles, TMS is high (Resulting in a TAP reset). TMS changes to low with the falling edge of TCK. At this time the TDI signal is low. Your signals should be identical. Signal rise and fall times should be shorter than 100ns.

If your measurements of TCK, TMS and TDI (the signals output by J-Link / J-Trace) differ from the results shown, disconnect your target hardware and test the output of TCK, TMS and TDI without a connection to a target, just supplying voltage to J-Link's/J-Trace's JTAG connector: VCC at pin 1; GND at pin 4.