I can't figure out how to use this shift register

In summary, the user is having trouble getting the 1st output to output a zero on their 74hc595 shift register. They have studied the datasheet and tried connecting various inputs and outputs, but have not been successful. They are asked to provide a schematic of their circuit and are reminded to use the SCK and RCK inputs to properly transfer data to the shift register and its output register.
  • #1
David lopez
257
3
I bought a 74hc595 shift register.
The 1st output and 2nd output won't change. They turn on two diodes and none of them will turn off. How do you get the 1st output
To output a zero? I have studied the
Datasheet doesn't help.
 
Engineering news on Phys.org
  • #2
I can't figure out how to help you because you have not provided much to go on. Can you provide a schematic of your circuit? Did you overstress the SR? Hopefully you didn't buy just one.
 
  • #3
I think this file has a schematic of shift register.
 

Attachments

  • 46105 (1).pdf
    93.4 KB · Views: 136
  • 46105 (1).pdf
    93.4 KB · Views: 150
  • #4
David lopez said:
I think this file has a schematic of shift register.
That's not what was asked for, that's just the shift register. What is YOUR circuit than includes the shift register? If you have nothing but the SR, it will just sit there like a lump.
 
  • #5
I connect output q0 and output q1 to
Leds. I connect ser input to negative
Terminal. G input to negative terminal.
I connect sclr input to positive terminal
To pulse high. I briefly connect sck input to positive terminal to pulse high.
 
  • #6
You must use SCK to edge clock SER data into the 8 bit serial register.

You must then clock PCK once to transfer all 8 serial data bits into the parallel output register.

If you enable the drivers with Gbar, and disable reset SCLbar, then data will then appear on the outputs,
 
  • #7
Once you have loaded bits into the shift register (the first column of flip-flops on pg.2 of the data sheet) with SCLK, you must then transfer those bits to the second column of flip-flops by toggling the RCK input, pin 12.

The reason for the second column of flip-flops is to keep the output data constant while shifting in new data. The RCK loads the data from the first column into the latches of the second column.

Cheers,
Tom
 

1. How does a shift register work?

A shift register is a digital logic circuit that can store and shift data bits in a sequential manner. It consists of a series of flip-flops connected in a chain, with each flip-flop storing one bit of data. When a new bit is added to the shift register, the existing bits are shifted to the next flip-flop, creating a new space for the new bit to be stored.

2. What is the purpose of a shift register?

A shift register is commonly used in digital systems to expand the number of output pins available on a microcontroller or to store and shift data in a specific order. It is also useful for serial-to-parallel and parallel-to-serial data conversion.

3. How do I connect a shift register to other components?

To connect a shift register to other components, you will need to connect the input pins to a microcontroller or other source of data, and the output pins to the components you want to control. You will also need to connect the clock and reset pins to appropriate signals.

4. What is the difference between a serial-in, parallel-out shift register and a parallel-in, serial-out shift register?

A serial-in, parallel-out shift register receives data one bit at a time and outputs multiple bits in parallel. A parallel-in, serial-out shift register receives multiple bits in parallel and outputs them one bit at a time. The direction of data flow is the main difference between these two types of shift registers.

5. What are some common applications of shift registers?

Shift registers are commonly used in digital circuits for data storage, data transfer, and data manipulation. They are also used in serial communication protocols, such as SPI and I2C, and in LED displays to control the lighting of individual LEDs. Other applications include frequency division, data encryption, and data compression.

Similar threads

  • Electrical Engineering
Replies
14
Views
740
  • Engineering and Comp Sci Homework Help
Replies
10
Views
1K
  • Electrical Engineering
Replies
10
Views
1K
Replies
2
Views
1K
  • Electrical Engineering
Replies
13
Views
3K
  • Electrical Engineering
Replies
3
Views
1K
Replies
3
Views
445
  • Electrical Engineering
Replies
5
Views
5K
Replies
1
Views
2K
Replies
12
Views
2K
Back
Top