Applying JTAG

Applying JTAG for Field Service

Once a product ships, the role of JTAG does not end. Periodic software and hardware updates can be performed remotely using the JTAG chain as a non-intrusive access mechanism. This allows Flash ROM updates and reprogramming of programmable logic for example. Service centers that normally would not want to invest in special support equipment to support a product, now have an option of using a standard PC or lap-top for JTAG testing. A simple PC based JTAG controller can be used for all of the above tasks and also double as a fault diagnostic system, using the exact same test vectors that were developed during the design and production phase. This concept can be taken one step further by allowing an embedded processor access to the JTAG chain. This allows diagnostics and fault isolation to be performed by the embedded processor. The same diagnostic routines can be run as part of a power-on self-test procedure.