Boundary Scan Intelligent Diagnostics (BSID) Overview

The Boundary-Scan Intelligent Diagnostics (BSID) module generates diagnostics for two kinds of boundary-scan tests: Virtual Interconnect Test (VIT), and Virtual Component and Cluster Test (VCCT).

BSID can be run on either the Eclipse Test Development environment or the ScanExecutive Manufacturing  test system. When a boundary-scan test fails, BSID uses the diagostic failure data database generated by the ATPG module and the digital test results generated by the tester to isolate the failing devices, devicepins and the networks involved.

Virtual Interconnect Test diagnostics

VIT tests can fail under a variety of conditions. BSID diagnoses the following failure types. In all cases, BSID clearly states the problem, lists all inputs and outputs on the net, and identifies the failing detect points.

All inputs on a net are stuck either at a logic 1 or a logic 0. Typically, the problem is an open on the net or the net is shorted to power or ground.

Some inputs on a net are stuck either at a logic 1 or a logic 0. This condition typically results from an open on the part of the net that connects the stuck input(s).

Net is stuck either at a logic 1 or a logic 0 only when a particular driver is active. Most often, the problem is an open at the specified driver lead on a bus.

Shorts between nets

Common bridging faults between nets are clearly diagnosed Many testers and simulators accept truthby BSID regardless of whether a logic 1 or a logic 0 wins.

Strong driver short

Typically, a high current driver or a tester pin is shorted to some other net(s). The prob-lem is that the net with the strong driver never fails because it overdrives other net(s) involved in the short.

Faulty bidirectional pin

This failure type is typically caused by a blown input or output driver at the bidirectional pin. As a result, the boundary-scan output cell for the bidirectional pin drives the correct data onto the net but its associated boundary-scan input cell does not capture the correct value. Alternatively, the boundary-scan input cell captures the correct value from other drivers on the net, but its associated boundary-scan output cell is not able to drive the net.

Extended stuck-at faults

Leaky bus drivers can cause a test to fail by overdriving the active driver on a bus. Shorts between boundary-scan nets and non-boundary-scan nets. As part of an in-circuit test program, BIT Plus patterns can detect shorts between boundary-scan nets that have no tester access and non-boundary-scan nets with tester access.

To generate diagnostics for the internal connections of a virtual cluster test, BSID uses fault-dictionary techniques and must be supplied with a fault-dictionary database.

Benefits

• Automatic diagnosis of VIT Eclipse ATPG and VCCT test failures
• Can be run on the tester or at an off-line repair station
• Currently available for Teradyne board test systems and Intellitech test systems
• Transportable to other test systems