ULINK: CHAINING JTAG DEVICES

Information in this article applies to:

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

QUESTION

I have used ULINK on a evaluation board with no problems. Now I have got the real hardware where there is an FPGA(EP1K30) in the JTAG chain. It does not work. What is required to allow chained devices on the JTAG bus?

ANSWER

ULINK supports device chaining on the JTAG bus. But a JTAG device must have the following attributes to allow chaining:

• BYPASS register must be implemented for chaining.
• After reseting TAP the IDCODE must be the default instruction
• Bit 0 of ID Code must be 1.
• In CAPTURE-IR state the fixed value 1 must be loaded into the IR.

If the automatic setup does not work, you may manually setup the attributes of the device. In this case only BYPASS register must be implemented for chaining.

MORE INFORMATION

• Refer to Chaining Multiple Targets in the ULINK User's Guide.

FORUM THREADS

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

• JTAG Device chain error

Last Reviewed: Sunday, January 28, 2007