View tc74hc251p datasheet:

TC74HC251P ********** IL00 C-MOS 8-LINE-TO-1-LINE DATA SELECTOR/MULTIPLEXER WITH 3-STATE OUTPUT —TOP VIEW— 4 Y0 VDD Y3 IN 1 16 3 Y1 (+2 to +6 V) 2 Y2 Y2 IN 2 15 Y4 IN 1 Y3 5 YC 15 Y4 Y1 IN 3 14 Y5 IN 14 Y5 6 YC 13 Y6 Y0 IN 4 13 Y6 IN 12 Y7 YC OUT 5 12 Y7 IN A B C INH 11 10 9 7 YC OUT 6 11 A IN INH IN 7 10 B IN 8 9 C IN CONTROL IN OUTPUT GND C B A INH YC YC X X X 1 HI-Z HI-Z 0 0 0 0 Y0 Y0 0 0 1 0 Y1 Y1 0 1 0 0 Y2 Y2 0 1 1 0 Y3 Y3 1 0 0 0 Y4 Y4 1 0 1 0 Y5 Y5 1 1 0 0 Y6 Y6 1 1 1 0 Y7 Y7 0 ; LOW LEVEL 1 ; HIGH LEVEL X ; DON'T CARE HI-Z ; HIGH IMPEDANCE