Setting up the JTAG Chain

To ensure a test system is reliable and free from random failures, it is important to design the JTAG interface circuit with care. Ensuring the correct high-speed terminations are in place, implementing suitable grounding and pin-out, creating a Test Reset Sequence, and verifying signal integrity are all essential steps that must not be skipped.

The following 7-step sequence should be followed to create a robust test system:

Figure 1: Method for JTAG chain setup

This section of the user-guide provides a detailed explanation of the following points and why they are necessary:

• How to implement the ground returns for JTAG signals
• The best pin-out for the JTAG connector and why it is important
• Implementing the necessary JTAG terminations
• Using JTAG Chain Debugger to check DC voltages
• Creating a Pin Mapping and a Test Reset Sequence
• Performing a low speed chain check
• Checking the maximum speed of operation and how to optimise signal integrity