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.