Signal testing apparatus for large circuits - has cell chain operating in normal mode to supply analog- digital signal to digital circuit and digital-analog signal to analog circuit and in test mode analog circuit is decoupled from digital circuit

摘要

The apparatus has a mixed signal circuit containing an analog circuit (4) to detect analog-to-digital signals and a digital circuit (10) to detect digital-to-analog signals. A boundary scan cell chain (50) connected between the two circuits receives the control signals. The cell chain operates in normal mode or in test mode depending on the control signals. - Each analog-to-digital and digital-to-analog signals detected by the analog and digital circuits respectively are detected by the cell chain. In the normal operating mode, the analog-to-digital signal is supplied to the digital circuit and the digital-to- analog signal is supplied to the analog circuit. In the test mode, the analog circuit is decoupled from the digital circuit.