The 74F398 and 74F399 are the logical equivalents of a quad 2-input multiplexer feeding into four edge-triggered flip-flops. A common Select input determines which of the two 4-bit words is accepted. The selected data enters the flip-flops on the rising edge of the clock. The 74F399 is the 16-pin version of the 74F398, with only the Q outputs of the flip-flops available.
■ Select inputs from two data sources
■ Fully positive edge-triggered operation
■ Both true and complement outputs—74F398