The 74HC595 is a commonly used general
purpose shift register available in DIP16, SSOP16 / TSSOP16, and QFN
packages. A shift register is composed of one or more latch circuit
called stages which when fed data input, move their current contents to
the next register in line and accept the new data. Repeating this 8
times fills the 8-bit register with a byte of information (8 bits)
allowing for a parallel output on pins Q0 -Q7. In microcontrollers
where space, and consequently pins, are limited, a shift register, such
as the 74HC595 can be used to allow just a few pins of the
microcontroller to control a larger (possibly much larger) amount of
lines (such as 8 LEDs) in the picture above. Additionally shift
registers can be used as buffers for fast transmission between circuits
when reception time is brief and periodic, such as in the transfer
stream of a sound playback device with serial I/O FLASH memory. The
shift register can buffer, to an extent, the data (composed of bits)
and dump the contents rapidly to the control processor in a single
clock cycle.
Features:
8-bit serial input
3-state outputs
100MHz shift frequency
Serial I/O or Serial In - Parallel Out (For use as a serial to parallel
data converter)
Asynchronous reset allows all (8) eight stages to be cleared
simultaneously.