Abstract: A boundary scan cell includes a shift latch, an update latch and a flushable latch that each have at least a respective data input and at least a respective data output. The data output of the shift latch is coupled to the data input of the update latch. The boundary scan cell further includes control circuitry that controls operation of the flushable latch circuit. The control circuitry selects, as input data for the flushable latch, one of a functional logic signal and a boundary scan signal in response to a mode signal. If the mode signal indicates a test mode, the control circuitry selects the boundary scan signal as the input data and causes the flushable latch to flush through the input data to the data output of the flushable latch independent of a system clock signal. The boundary scan cell can be implemented as either an input or output cell and preferably is compliant with IEEE Std 1149.1.

Abstract: A circuit is disclosed that includes a latch circuit and boundary scan cell circuitry. The latch circuit includes a slave latch and a master latch having a data output. The slave latch includes at least a first data input connected to the data output of the master latch, a second data input, and a control input that receives a control signal that controls latching of data present at the second data input. The boundary scan cell circuitry is connected to the second data input and to the control input of the slave latch so that the boundary scan cell circuitry can supply the control signal and data to the slave latch. In one embodiment, the boundary scan cell circuitry is IEEE1149.1-compliant and the circuit further includes either an output driver coupled to the data output of the slave latch or an input receiver coupled to a data input of the master latch.