The SN54 / 74LS168 and SN54 / 74LS169 are fully synchronous 4-stage up/down counters featuring a preset capability for programmable operation, carry lookahead for easy cascading and a U / D input to control the direction of counting. The SN54 / 74LS168 counts in a BCD decade (8, 4, 2, 1) sequence, while the SN54 / 74LS169 operates in a Modulo 16 binary sequence. All state changes, whether in counting or parallel loading, are initiated by the LOW-to-HIGH transition of the clock.