On-chip logic includes a shadow register cross-coupled with a multiple input shiftsignature register. Using multiple data packet signal testers with narrower receiver bandwidths to process respective portions of the wider bandwidth of the data packet signals produced by the devices under test enables use of lower cost, narrower-bandwidth test equipment to test wide-bandwidth signals. The subscriber to infrastructure station message is composed so that it occupies the first m codewords and contains a header that describes the length of the subscriber to infrastructure station message. The first poly extends from a device region to a strap region, and extends substantially parallel to a first length of the second poly.