Patent ID: 7743294

Claim:
Apparatus for processing data, said apparatus comprising: a first diagnostic unit configured in a first diagnostic mode to communicate first diagnostic data with an external diagnostic device in accordance with a first data communication technique; a second diagnostic unit configured in a second diagnostic mode to communicate second diagnostic data with said external diagnostic device in accordance with a second data communication technique; one or more diagnostic data connections coupled to both said first diagnostic unit and said second diagnostic unit and configured to provide diagnostic data communication between said apparatus and said external diagnostic device; and a watcher unit coupled to at least one of said one or more diagnostic data connections and configured in response to detection of a predetermined signal pattern at said at least one of said one or more diagnostic data connections to switch between said first diagnostic mode and said second diagnostic mode, wherein said watcher unit is responsive to a first predetermined signal pattern to switch from said first diagnostic mode to said second diagnostic mode and is responsive to a second predetermined signal pattern, different from said first predetermined signal pattern, to switch from said second diagnostic mode to said first diagnostic mode, and wherein said first diagnostic unit is a JTAG diagnostic unit and said JTAG diagnostic unit includes a JTAG TAP controller state machine having states corresponding to a Test-Logic-Reset state, a Run-Test/Idle state, a Select-DR state, a Select IR state, a shift state, an update state and a capture state and said first predetermined signal pattern triggers state changes within said JTAG TAP controller state machine that move between said Test-Logic-Reset state, said Run-Test/Idle state, said Select DR state and said Select IR state without entering any of said shift state, said update state and said capture state.