Techniques are provided for capturing external signals at output pins on a
programmable logic integrated circuit (IC) during a boundary scan test. A
JTAG sample signal is routed to an input/output block on a chip and
active during a JTAG sampling phase. An input buffer coupled to an output
pin is turned on during the JTAG sample phase. Logic gates enable the
input buffer in response to the JTAG sample signal so that the input
buffer can capture a signal on the pin. The input buffer is turned off
after the JTAG sampling phase to conserve power. The output buffer
coupled to the pin that receives the test signal is tristated to prevent
contention during the JTAG sampling phase. The techniques of the present
invention can be used to test board level interconnects in less time and
are easy to implement.