Low overhead input and output boundary scan cells
AssigneeTexas Instruments Incorporated
InventorLee D. Whetsel
Life of this patent
Estimating the term…
Abstract
An integrated circuit includes functional circuitry for performing normal operating functions of the integrated circuit, an output terminal which is accessible externally of the integrated circuit, and an output drive circuit (OB,OA) for receiving an output signal from the functional circuitry and driving the output signal to the output terminal. A switch (TG1,S1) is provided for selectively isolating the output terminal from the functional circuitry, and the switch is connected between the functional circuitry and the output drive circuit.
Claims24
A method of operating an integrated circuit having functional circuitry for performing normal operating functions of the integrated circuit and output circuits for receiving output signals from the functional circuitry and driving the output signals to output terminals of the integrated circuit, comprising the steps of:
- powering up the integrated circuit with the output circuits disconnected from the functional circuitry;
- inputting a test signal to the output circuits and thereafter observing whether an expected response to the test signal occurs at the output terminals;
- setting a drive strength of one of the output circuits to a drive strength level that is less than a fill drive strength level thereof;
- and
- connecting the output circuits to the functional circuitry only if the expected response is observed.
A method of operating an integrated circuit having functional circuitry for performing normal operating functions of the integrated circuit and having output circuits which include respective inputs for receiving output signals from the functional circuitry and which output circuits drive the output signals to output terminals of the integrated circuit, comprising the steps of:
- powering up the integrated circuit with the output circuits disconnected from the functional circuitry but with the output circuits still capable of driving to the output terminals signals received at the inputs;
- inputting a test signal to the inputs of the output circuits and thereafter observing whether an expected response to the test signal occurs at the output terminals;
- and
- connecting the output circuits to the functional circuitry only if the expected response is observed.
A method of operating an integrated circuit having functional circuitry for performing normal operating functions of the integrated circuit and having output circuits which include respective inputs for receiving output signals from the functional circuitry and which output circuits drive the output signals to output terminals of the integrated circuit, comprising the steps of:
- powering up the integrated circuit with the output circuits disconnected from the functional circuitry but with the output circuits still capable of driving to the output terminals signals received at the inputs;
- and
- inputting a test signal, to the inputs of the output circuits and thereafter observing whether an expected response to the test signal occurs at the output terminals.
Dependencies are inferred from the claim text.