Shift Register 8-Bit - 74HC595

From bildr

Manufacturer: TI
Voltage: +2 to +6 V
Doc Sheet

The 74HC595 is a simple 8-bit shift register IC. Clock in data and latch it to free up IO pins on your micro. Its output allows you to daisy-chain multiple chips together without requiring additional inputs from the microcontroller. Essentially, data is clocked in bit by bit, with

Q A

taking the value of each input bit (either HIGH or LOW). Every time

Q A

takes on a new input value, it first passes on its previous value to

Q B

, which passes its previous value to

Q C

, etc. The value in

Q H

is discarded, unless the output pin (

Q H'

) is utilized, in which case, it is passed on to a daisy-chained register.

Hooking it up

Pins
- VCC - input voltage (+2 to +6 V)
- GND - ground
- $Q A, Q B, ... Q H$ - 8 outputs
- SER - serial input, hooks up to the serial output of your microcontroller
- OE - output enable (when high, outputs are in high impedance state)
- SRCLK - shift register clock (positive edge triggered); it times the input to SER
- SRCLR - overriding clear input (low state to clear register)
- RCLK - storage register clock (positive edge triggered); it is used to latch the register to the outputs
- $Q H'$ - output for communication to pass bytes on to additional chips

Unless there is a need to use additional digital pins to control output enable or shift register clear, connect OE to ground and SRCLR to +5V for normal operation.