| 摘要 |
A method in which the boundary-scan circuitry of a boundary-scan chain is placed in a first condition in which each bit of a series of bits will traverse a path through an equipment identification register if one exists or will require one clock to traverse each device in the boundary-scan chain in which no complete identification register exists. A first recognizable series of bits is sent through the chain and the beginning of the series of bits is detected at the output of the chain while a count is kept at the output to determine the number of individual boundary-scan circuits in the chain. The count is incremented by one for each identification register traversed or for each circuit which has no such complete register. The boundary-scan chain is then placed in a second condition in which each bit of a series of bits will traverse the instruction registers of the individual boundary-scan circuits in the boundary-scan chain, and a second recognizable series of bits is sent through the chain and counted until the a detectable portion of the second series of bits appears at the output of the boundary-scan chain. This count indicates the total number of bits in the instruction registers in the chain.
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