The 'HC597 and CD74HCT597 are high-speed silicon gate CMOS devices that are pin-compatible with the LSTTL 597 devices. Each device consists of an 8-flip-flop input register and an 8-bit parallel-in/serial-in, serial-out shift register. Each register is controlled by its own clock. A "low" on the parallel load input (PL) shifts parallel stored data asynchronously into the shift register. A "low" master input (MR) clears the shift register. Serial input data can also be synchronously shifted through the shift register when PL is high.