Apparatus and method for discrete test access control of multiple cores

1. An electronic circuit, comprising:

a test access protocol machine with a core address register to receive and store a core address and a signal routing control circuit to address a selected computational core, of a set of computational cores, as specified by the core address stored in the core address register and to route output test data from the selected computational core, wherein the signal routing control circuit applies control signals to a set of multiplexers and logical gates to address selected computational cores and wherein signal routing control signals control an output multiplexer to route the output test data from the selected computational core.

2. The electronic circuit of claim 1 wherein the signal routing control circuit generates an enable signal to facilitate application of a test clock signal to the selected computational core.

3. A method, comprising:

forming a test access protocol machine to selectively access a single core of a multiple core system as specified by a core address stored in a core address register; and

operating the test access protocol machine in a first state wherein output test data from the single core is directly delivered to the test access protocol state machine and in a second state wherein output test data from the single core is daisy chain routed through at least one additional core of the multiple core system prior to being delivered to the test access protocol state machine.

4. The method of claim 3 wherein operating includes generating a first multiplexer control signal to establish the first state and producing a second set of multiplexer control signals to establish the second state.

5. The method of claim 3 further comprising loading an address for the single core into the test access protocol state machine.