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89
74HC595 IC:
The shift register operates in a fairly simple way, but can be modified to
become very complicated but very useful.
We can control the shift of the register with clock pulses.
As we raise the signal going to the clock pin to high, the clock is moved
forward one step, and when we pull it low and high again it shifts another.
Each time we shift the clock we switch the input to a different one of the
eight registers.
We are essentially controlling the output of each of the eight pins one at a
time, and as we move one clock signal forward, we switch to the next
output pin to control.
The shift register can be a great tool when you are short on output pins,
taking 8 outputs from only about 3 actual data inputs.
It can be added to for some really complicated applications, and they can be
daisy-chained together for even more output options.
In this project, we only use three I\O ports to control a, b, c, d, e, f, g and dp,
therefore control the segment display.
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