| 摘要 |
PURPOSE:To measure easily the state of a latch or a flip-flop existing within an LSI from outside by adding a small number of scan terminals. CONSTITUTION:When a scan indicating flip-fop SCF/F3 is set, a counter 4 starts to count clocks CLK. The output of the counter 4 is supplied to a selector 5. Thus the selector 5 selects successively the outputs of flip-flops 7-0-7-255 having corresponding numbers and delivers them to an output terminal 2. Thus an output terminal 2 can record and measure the states of the flip-flops 7-0- 7-225 contained in the LSI at and after a time point when a scan start indication pulse is supplied to an input terminal 1. Furthermore the holding signals are applied to the flip-flops 7-0-7-225 via OR gates 8-0-8-225 to hold their states in a scan mode. |
