Multi-Voltage JTAG Chain

As low-power, handheld devices become more prevalent, printed circuit
boards with a mixture of 5-V, 3.3-V, 2.5-V, and 1.8-V devices have
become common, making the design of a JTAG chain challenging. The
designer must determine both the operating voltage and the order to
place devices that operate at different voltages. This article provides
some tips and techniques for making a robust design.