and linked tap 1 becomes unlinked while the test bus transitions from the updatedr state to the run test idle state to the select dr scan state the link change occurs on the falling edge of the tck in the updatedr state with en 1 of tap 1 going low and en 2 of tap 2 going high on the next rising tck edge the test bus transitions into the run test idle state tap 1 now unlinked is forced to transition to run test idle see fig9 and tap 2 now linked remains in run test idle see fig9 on the next rising tck edge the test bus transitions to the select dr scan state tap 2 transitions with the test bus to the select dr scan state and tap 1 remains in the run test idle state fig1 shows a timing example wherein unlinked tap 2 becomes linked and linked tap 1 becomes unlinked while the test bus transitions from the updatedr state directly to the select dr scan state the link change occurs on the falling edge of the tck in the updatedr state with en 1 of tap 1 going low and en 2 of tap 2 going high on the next rising tck edge the test bus transitions into the select dr scan state tap 1 is forced to transition to run test idle see fig9 and tap 2 transitions with the test bus from run test idle to the.