The 74HC595; 74HCT595 is an 8-bit serial-in/serial or parallel-out shift register with a storage register and 3-state outputs. Both the shift and storage register have separate clocks. The device features a serial input (DS) and a serial output (Q7S) to enable cascading and an asynchronous reset MR input. A LOW on MR will reset the shift register.

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Pin Configuration

Features

• 8-bit, Serial In – Parallel out Shift register
• Operating Voltage: 2V to 6V
• Power Consumption: 80uA
• Output source/sink current: 35mA
• Output Voltage is equal to Operating voltage
• Minimum high-level Input Voltage: 3.15V @(Vcc=4.5V)
• Maximum low-level Input Voltage: 1.35V @(Vcc=4.5V)
• Can be easily cascaded with more IC to get more outputs
• Maximum Clock Frequency: 25Mhz @4.5V
• Available in 16-pin PDIP, GDIP, PDSO packages

Note: Complete Technical Details can be found in the 74hc595 datasheet given at the end of this page.

Alternatives Shift Registers

Where to Use 74HC595 IC

The 74HC595 is an 8-bit Serial In – Parallel Out Shift Register, i.e. it can receive (input) data serially and control 8 output pins in parallel. This comes in very handy where do not have enough GPIO pins on our MCU/MPU to control the required number of outputs. It is often used in projects where relatively a large number of LED’s has to be controlled through the Microcontroller. It can also be used to interface LCD screen since they can acts as the data bit for the LCD displays. It can also be used to control 5V loads like relays through a 3.3V microcontroller since the high-level voltage is only 3.15. So if you are looking for an IC to save on your GPIO pins on the Microcontroller then this IC might be the right choice for you.

How to Use a 74HC595 IC

The 74HC595 shift register is commonly used with microcontrollers or microprocessors to expand the GIPO functionalities. It requires only 3 pins connected to the MCU, which are Clock, Data and Latch. It has a wide operating voltage from 2V to 6V. An application circuit of the IC is shown below:

The pins 11, 14 and 12 are connected to the GPIO pins of the Microcontroller. In which pin 11 is the clock which sends a constant pulse to keep timing. The pin 14 is Data which actually sends the Data about which output pins has to stay low and which should go high. The Pin 12 is the Latch which updates the received the data to the output pins when made high, this pin can also be permanently held high. The below image will help you understand better.

As you can see the clock is continues train of pulses, and the data goes high only at the respective place where the output has to get high. Here for example the binary value 0b10110011 is passed to the microcontroller. The pin Master reset (MR) is used to reset the outputs, when not in use it is held high to vcc, similarly the pin should be held low when not in use.

Another important advantage of the 74hc595 IC is that it can be cascaded to control more than 8 outputs. To do this we use the Q7’ (pin 9), this pin should be connected to the data pin of the second 74HC595 IC. This way the first 8-bit sent from MCU will be used by the 1st IC and the second 8-bit will be used by the 2nd IC.

Applications

• Expand the GPIO pin on a MCU/MPU
• LED Matrix/Cube Projects
• Interface LCD
• Cascading applications
• High logic level controller

Serial Vs Parallel

2D Model of 74HC595 (PDIP)

Hello everyone! I hope you will be absolutely fine and having fun. Today, I am going to explain all of you about Introduction to 74HC595. It is basically a shift register. It has an ability to store and to shift the data of 8 bits. First of all the data is written on the register serially and then it goes to the storage register. All of the output lines are controlled by this register.

74HC595 register is a very high speed device based on Complementary Metal Oxide Semiconductor (CMOS). 8 bit data register receives the data from the input DS. This data is then transferred from the input shift register to the output shift register. 74HC595 has a vey wide range of applications in daily life. It can be used as serial to parallel data converter, can receive and keeps the data for a long time etc. Moreover, It can be used in home appliances, for the industrial management, as computer peripheral. We will discuss further about this register later in this tutorial.

Introduction to 74HC595

74HC595 is a shift register having and eight bit storage register and an eight bit shift register. The data is written first and then stored into the device. It is high speed CMOS device. The data is usually entered in a serial format. Storage register is used to control the output lines of 74HC595. It has different real life applications e.g. in home appliances, computer peripherals, serial to parallel converter etc.

1. 74HC595 Pinout

• It has 16 pins in total out which eight are on left side and the remaining on the right side of the structure.
• The different function is associated with each of the pin.
• Some of the pins acts as an input to this device and receives data serially and transfer to the output pins to observe the received data.
• The pin diagram for 74HC595 is shown in the figure below:

• DS pin acts and receives the serial data.
• All of the lines with prefix Q acts as the output lines.

2. 74HC595 Pin Configuration

• In this section if the tutorial Introduction to 74HC595, I will tell you about the functions associated with each of the individual pin of 74HC595.
• All of the associated functions are describes in the table given below.

3. Functioning Diagarm

• The proper functional diagram of the shift register 74HC595 is shown in the figure below.

• From the above figure you can see that SHCP, master reset (MR) and the input DS are connected to 8 stage shift register.
• Pin number 12 i.e. STCP is connected to 8 bit storage register.
• The output enable (OE) is connected to 3 state outputs.

4. 74HC595 Functional Description

• In this section of the tutorial Introduction to 74HC595, I will tell you about the functions of each line of the 8 bit shift register 74HC595.
• Complete description of the functions of 74HC595 is given in the table shown below.

5. 74HC595 Timing Diagram

Serial To Parallel Converter

• The arrow in the upward direction shows the rising edge of the each wave either received or applied.
• The shape of the signals applied and received and their relation with each other is shown in the figure below.

5. 74HC595 Logic Diagram

• The logic diagram for 74HC595 8 bit shift register is shown in the figure below.

• You can see that there are 8 different stages from 0 to 7 and latches are there in the logic diagram of 74HC595.
• Output enable (OE) and master reset (MR) are connected to latches with an inverted sign usually known as bubble.

6. 74HC595 Current/Voltage Rating

• The current, power and voltage rating along with their values and system international units are shown in the table given below.
• The values of operating temperature and storage temperature are also shown in the figure below.

7. 74HC595 Proteus Simulation

• I have a Proteus simulation for continuous control of the different LED’s using 74HC595.
• The screenshot of the simulation is shown in the figure below.

• The complete Arduino source code is shown below.
• You need to just upload .hex file of this code into the Arduino of Proteus and run the simulation.

• The running form of the above simulation is shown in the GIF below.

• You can download the complete simulation as well as the complete Arduino source code, here by clicking on the button below.

• Just download .rar file, extract it and enjoy the complete package having both Arduino source code as well as Proteus simulation.

So that is all from the tutorial Introduction to 74HC595. I hope you really enjoyed this tutorial. If you face any sort of problem regarding any thing, you can ask me anytime in comments without even feeling any kind of hesitation. I will try my level to entertain you and to solve your issues in a better way, if possible. Our entire team is 24/7 here to entertain you and to solve your issues in a way or the other. I will explore different IC’s in my later tutorials and will surely share all them with all of as you as well. So, till then, Take Care 🙂

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