It is only made available when all 8 bits are in their required positions. Remember latch is separate from the shift register so data shifting is not available on latch during shift phase. Until this function is called the latch contains the data that was loaded last time by pulsing the store clock signal.

When all bits have been transferred this function is called to make the data available on output. This function moves the data in the shift register to the latch using a pulse on store clock line. This function sends a pulse to the Shift Clock. HC595DataLow() – Makes the data line low (0) HC595DataHigh() – Makes the data line high (1) The only this this function does is to set the i/o lines of the MCU that connects to 74HC595 as output. Initializes the shift register sub-system. In this tutorial we will learn about the output shift register IC 74HC595, develop routines for AVR in avr-gcc, and finally test those routines using a simple example. We will describe input shift register in latter tutorial. In this way they wisely saved money and increased the reliability of the joystick (thin cable, less wires and better connector).

Instead they put a input shift register on the joystick and used 5 pins for data transfer. Their are 8 buttons (you will notice 10 but 2 of it are turbo, that means they repeat action A or B(turbo A or B pressed) at particular frequency when kept depressed) The designers didn’t ran 9 pins from the consol to the joystick (approx 1.5 meters). The most common commercial example I found is the NES joystick.

It takes parallel input and transfer it serially to the MCU. It does reverse of the output shift register. The above described what we called an output shift register.

Say if you want to control 50 leds that are at the distance of 2 meter from the controller then you save lots of wires! and mess up too!.

Only three i/o lines can drive virtually any number of output ports.

The idea is to use a shift register, a shift register help us load data in a serial fashion (requiring less number of i/o lines) and then convert the data into a parallel form that can drive many types of load like LED,Relays, motor etc, just like normal i/o ports of MCU. The technique is to expand the number of input and output lines available in any microcontroller. Today I am going to explain a helpful technique used while designing embedded system.

74hc165 hardware spi atmega