An identification (ID) process comprises in each of a plurality of bit times, a debug test system asserting a control signal at a predefined state to a plurality of target systems, and each target system, having a bit pattern and the bit patterns being different among the target systems, outputting a bit from its bit pattern on the control signal. The process further comprises each target system comparing the resulting state of the control signal to that target system's output bit. If the target system's output bit differs from the resulting control signal state, the target system ceases participating in the ID process or, if the target system's output bit matches the resulting control signal state, the target system continues to participate in the ID process.