The clock for the six decade counter (digit positions 3-8) is formed from the internal `OR' combination of B4/D2 and B8/D2 if LS7031 is used with external prescaling counters. When operated in this fashion the maximum allowable propagaton delay between B4/D2 (H-L) and B8/D2 (L-H), measured at Vss - 1V, is 10ns. If used as a straight six decade counter, clock pulses may be applied to inputs B4/D2 or B8/D2 with the unused input held low. In either mode of operation total pulse width must be minimum 62ns. See Block Diagram.