| 摘要 |
PURPOSE:To test an LSI from the outside easily and properly by a method wherein a selective changeover circuit which selects one of the output of an A/D converter and the output of another system is provided in the LSI in which the A/D converter and the system are contained. CONSTITUTION:A selective changeover circuit 4 is contained in an LSI 1 in addition to original functions such as an A/D converter 2 and a system 3. The selective changeover circuit 4 selects one of the output Dout of the A/D converter 2 and the output Sout of the system 3 and leads it out to the external terminals (p) of the LSI 1. At the same time, one independent input terminal TP is added in order to introduce a changeover control signal Ts which sets and operates the changeover position of the selective changeover circuit 4 from the outside. With this constitution, both of the output Sout of the system 3 and the output Dout of the A/D converter 2 can be directly observed and tested from the outside of the LSI 1 by a tester 5 simply by operating the selected position of the selective changeover circuit 4. |
