Xilinx, Inc.

Brian Sadler

Tuyet Ngoc Simmons

Mohsen Hossein Mardi

David M Mahoney

Andrew W Lai

Michael Leonard Simmons

A test setup is provided to test differential signals outputs from the I/O block (IOB) pairs in an integrated circuit (IC). The test setup allows elimination of the external 100 Ohm resistors provided across the differential outputs on a device under test (DUT) test board containing the IC by taking advantage of a 100 Ohm resistor built into the IC between a portion of the IOB pairs. An IOB pair being tested may have its differential output terminal pair shorted to the differential output terminal pair of the IOBs having the internal 100 Ohm resistor.

Testing differential signal standards using device under test's built in resistors

Testing an integrated circuit having programmable logic is described. Programmable logic is configured as a daisy-chain of registers (-through-(N+1)) in a closed input/output loop to register a logic 1 and logic 0s. The logic states are circulated around the closed input/output loop. Operation of output blocks (-through-N) is controlled responsive to a series of outputs (-through-N) provided from a portion of the daisy-chain of registers (-through-N) to selectively place an output block of output blocks (-through-N) in an output mode responsive to the logic 1 output in the series of outputs while leaving the output blocks remaining in a non-output mode responsive to the logic 0s in the series of outputs. The output blocks (-through-N) are commonly coupled at an output node () for coupling to a single test channel, as only one output block is in the output mode at a time.

Test channel usage reduction

A method and apparatus for testing parasitic effects on conducting paths in high-speed systems using a test package which allows for very accurate measurements of the parasitic effects to be taken. The test package is designed to be nearly identical to the actual IC package and has an external connector to allow measurements to be taken through the package, instead of at a point close to the package.

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Brian Sadler