The ’HC595 contain an 8-bit serial-in, parallel-out shift register that feeds an 8-bit D-type storage register. The storage register has parallel 3-state outputs. Separate clocks are provided for both the shift and storage register. The shift register has a direct overriding clear (SRCLR) input, serial (SER) input, and serial outputs for cascading.
Both the shift register clock (RCLK) and storage register clock (SRCLK) are positive-edge trig- gered. If both clocks are connected together, the shift register is always one clock pulse ahead of the storage register.
The SN54HC595 is characterized for operation over the full military temperature range of –55°C to 125°C. The SN74HC595 is characterized for operation from –40°C to 85°C.