This project shows a way to hack a shift register in order to achieve efficient and fast results. Read through to know how to do this.
To input data to the microcontroller, the best way would be to use the parallel-in shift register brigade. Not only it is the easiest available way, but it is also the most efficient way to input a huge data to the microcontroller. But using a parallel-in shift registers has a drawback too. The drawback is that it would require some extra external pull up resistors and also it would not allow the external interrupts.
The benefits that would be provided by using the shift register brigade are they are fast and would require only three microcontroller pins. All these three microcontroller pins are multiplexed to the same line and a resistor has been provided to the data pin in order to let the shift register be driven by the clock without conflicting the data line
To avoid the time taken for processing, it is advisable to use the data pin register and according to the size of the data pin, the pull ups that would come across the process of reading the data from the board should be disabled. The key point while switching on or off the pull ups that it should be done after the I/O pin is set to the input.