These devices are positive-edge-triggered D-type flip-flops. The HCT377 devices are similar to the 'HCT273 devices, but feature a latched clock-enable (CLKEN)\ input instead of a common clear.
Information at the data (D) inputs meeting the setup time requirements is transferred to the Q outputs on the positive-going edge of the clock (CLK) pulse if CLKEN\ is low. Clock triggering occurs at a particular voltage level and is not directly related to the transition time of the positive-going pulse. When CLK is at either the high or low level, the D input has no effect at the output. These devices are designed to prevent false clocking by transitions at CLKEN\.