IEEE 1149.1 does a great job testing for structural problems with conventional digital nets, but when it comes to LVDS or capacitively-coupled circuits, dot1 is incomplete. It can give false passes on LVDS and false failures on ac-coupled nets. That's the reason IEEE 1149.6 was developed, an extension to dot1 often called AC-EXTEST. It uses dot6-compliant devices at the transmitting and received ends of an advanced network to send and sense pulses of data. Any failure mode of an LVDS or capacitively-coupled network (for example, an open leg, shorted leg to ground, open capacitor, etc.) can be detected by the response to the data pulses.
JTAG ProVision detects the presence of dot6-compliant devices and automatically creates the advanced tests, along with precise diagnostics. Diagnostics clearly state where a defect has been detected and can be used by JTAG Visualizer to present a schematic and layout view of the faulty area.