AS91L1003U

The AS91L1003U is a one to 3-port JTAG gateway. It partitions a single JTAG chain into three separate chains. These separate chains can be optionally configured to operate as a single chain.

The AS91L1003U device is used to provide enhanced capabilities to the standard IEEE1149.1. It enables the IEEE1149.1 interface to be used in a true Multi-Drop environment without any additional signals. This Multi-Drop capability enables the standard IEEE1149.1 interface to be used not just for stand alone Printed Circuit Board (PCB) testing, but complete system testing including all PCBs within a system back plane environment.

The AS91L1003U provides the capability of partitioning the PCB into multiple smaller IEEE1149.1 scan chains totally under software control. Partitioning the IEEE1149.1 chains on the PCB has several benefits, which include easier fault diagnostics capabilities, as a fault on one of the IEEE1149.1 Local Scan Ports (LSPs) does not render the PCB un-testable, faster flash programming on the PCB's and removal of IEEE1149.1 signal loading issues.

All of the protocols required for addressing the AS91L1003U device via the Multi-Drop capability and the protocols for configuring which of the three IEEE1149.1 LSPs of the AS91L1003U are to be used, is handled via the 3^rd party ATPG tools from vendors like Asset-Intertech and JTAG Technologies. In a Multi-Drop environment, it is also possible to perform interconnect tests between multiple PCBs within the system thus extending the interconnect tests  to the back plane itself.