Low overhead input and output boundary scan cells

Claim 1

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.

Claim 2

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.

Claim 13

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.

Claim 14

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.

Claim 26

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.

Claim 27

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.