Scan path testing for logic IC - has inside at least one control point and at least one observation point for further conducting of external applied control point data

摘要

The control point data is laid at a corresp. control point for transfer of abservation point data, received at a corresp. observation point, and external output of the same. An individual data input connection(401) is provided for the input of selection data, for selecting a data transfer path for the series output of the observation point data. A sampling register(41) with a series circuit of at least one shift register is respectively connected with the control point and/or the observation point, and is arranged between the data input connection and the data output terminal, for them shift and holding of the control point data and the observation point data. A by-pass unit(42) is arranged between the data input terminal and the data output terminal, and forms a by-pass path for data, for by-passing the sampling register. A selection transfer hold unit(44) is arranged in parallel with at least one sampling register unit, for shifting and holding the selection data entered from the dat input terminal. A selector unit(43) selects either a register path formed by the sampling register or by-pass path, formed by the by-pass unit, as a transfer path of the control point data and the observation point data, and for connecting the selected paths with the data output terminal, on the basis of the selection data held by the selection data transfer-hold unit. ADVANTAGE - Reduces transfer time and required chip surface and number of connection pins