Patent ID: 7574641

Claim:
An integrated circuit, comprising: A. functional input pads and functional output pads; B. core circuitry having functional inputs and functional outputs respectively coupled to the functional input pads and functional output pads; C. an output buffer having an input that is coupled to a functional output and an output that is connected to one of the functional output pads; D. first and second test leads selectively connected to the one functional output pad through first and second test switches, the first and second test switches each having a control input; E. a third test lead selectively connected to the input of the output buffer through a third test switch, the third test switch having a control input; F. test access port circuitry including a test data input lead, a test data output lead, a test clock lead, a test mode select lead, and controller circuitry connected to the test data input lead, the test data output lead, the test clock lead, and the test mode select lead; and G. boundary scan circuitry connected to the test access port circuitry, the boundary scan circuitry including: i. a first scan path of boundary scan cells connected between the test data input lead and the test data output lead and coupling the functional input and functional outputs respectively to the functional input pads and functional output pads, and ii. a second scan path of switch control scan cells connected between the test data input lead and the test data output lead, each switch control scan cell having a switch control output, the switch control output of a first switch control scan cell being connected to the control input of the first test switch, the switch control output of a second switch control scan cell being connected to the control input of the second test switch, and the switch control output of a third switch control scan cell being connected to the control input of the third test switch.