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AR# 8255

3.1i JTAG Programmer - "Error: JTag - Boundary-scan chain test failed at bit position '3'..."

Description

Keywords: JTAG, integrity, failed, bit position, 2.1i

Urgency: Standard

General Description:
When I use the JTAG Programmer software to configure or perform other JTAG operations, an error message similar to the following is reported:

"Checking boundary-scan chain integrity...ERROR:JTag - Boundary-scan chain test failed at bit position '3' on instance 'ttt(Device1)'."

Solution

1

This error is the result of either a broken JTAG chain or noise on the chain.

Most commonly, the cable is not connected properly, a trace is not correct on the board, other devices in the chain are causing a problem, or a noisy parallel port exists.

Some suggestions for debugging are:

1. Try using a different PC and a different cable.
2. Probe the TAP to ensure that the signals are strong.

2

Verify that the PROG signal remains High during the JTAG Operations. If PROG is asserted low, the device resets itself and the JTAG chain is broken.

Xilinx recommends that the PROG signal have a pull-up resistor. (A 4.7k pull-up is suggested.) This pull-up is needed even if the PROG signal is connected to the CF signal of an XC18V00 device.
AR# 8255
Date Created 08/31/2007
Last Updated 09/30/2005
Status Archive
Type ??????