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• Vhdl Simulator Online
• 8 To 1 Multiplexer Verilog

This structural code instantiate the ODDPARITYTB module to create a - testbench for the oddparityTB design. The processes in it are the ones- that create the clock and the inputstream.Explore the design in the - debugger by either adding to the testbench to provide stimulus for the. I'm learning VHDL by myself using the book: ' Circuit Design with VHDL 1st ED ' by Volney Pedroni. I'm triyng to solve the first problem of chapter 5: Design a Generic Multiplexer, the objective is to creat a MUX of. A 'inputs' number of inputs with a 'size' bits length for each input, the input 'sel' choose the input that goes to the output. VHDL code for 8x1 multiplexer 07/15 - 07/22 (15) 07/08 - 07/15 (9) Unknown View my complete profile. Picture Window theme.

When we implement a digital hardware architecture, we often need to select an input to our logic between several different inputs. This selection logic is called digital multiplexer or MUX.

We name it digital multiplexer, to distinguish it from an analog multiplexer. An analog multiplexer implements the same function as digital MUX selecting the source of a signal from different analog source instead of digital.

As clear in Figure1, a MUX can be visualized as an n-way virtual switch whose output can be connected to one of the different input sources. On the left side of the Figure1, you can see the typical MUX representation. The number near the input ports indicates the selector value used to route the selected input to the output port.

VHDL implementation of a digital MUX

The digital MUX is one of the basic building blocks of a digital design. Using the VHDL we have basically two different ways to describe a digital MUX:

• Concurrent description
• Sequential description

Both the descriptions are totally equivalent and implement the same hardware logic. You can use concurrent or sequential depending on your coding style.

Here below is represented a 4-way mux using a sequential representation

MUX description using SEQUENTIAL VHDL statement

Here below is represented a 4-way mux using a concurrent representation of SELECT statement

MUX description using SELECT VHDL statement

Another VHDL description of a 4-way mux using a concurrent representation is given below

MUX description using simple CONCURRENT VHDL statement

In Figure 2, Figure 3, Figure 4, are reported the implementation on Cyclone IV FPGA of the sequential and concurrent implementation of the VHDL code reported above. As clear, the circuit implementation is the same for both different VHDL coding style even if the RTL view can be different.

VHDL – MUX implementation using an array structure

If the number of the MUX input is a power of two, we can take advantage of the VHDL syntax, implementing the MUX in a very compact VHDL description.

To take advantage of the power of two number of input, we use the VHDL array structure.

In the VHDL code below, we define a user type that is an array of a signal using the same VHDL type of the MUX input.

The selector signal will be used as the index of the array.

The VHDL code is very compact and efficient as we can see below.

MUX description using simple ARRAY VHDL statement

Figure 6 reports the RTL and technology view of the MUX implementation using the array architecture implementation. As clear, the final implementation is totally equivalent to the concurrent or sequential one.

MUX VHDL Simulation

Figure 6 shows the MUX implementation. The MUX output the input value depending on the selector signal

Conclusion

In this post, we addressed different ways to implement digital MUX in VHDL:

• VHDL Concurrent MUX implementation
• VHDL Sequential MUX implementation
• VHDL array based MUX implementation, when the input signals are a power of two

Heart booth online. All the different VHDL descriptions are mapped into the same hardware.

References

_{[1] https://en.wikipedia.org/wiki/Multiplexer}

_{[2] www.altera.com}

_{[3] www.xilinx.com}

_{[4] RTL HARDWARE DESIGN USING VHDL Coding for Efficiency, Portability, and Scalability – PONG P.CHU}

Part 1: Design of VHDL or Verilog

This tutorial shows the construction of VHDL and Verilog code that blinks an LED at a specified frequency. Both VHDL and Verilog are shown, and you can choose which you want to learn first. Whenever design code is written the FPGA designer needs to ensure that it works the way that it was intended. Despite your best efforts, there will always be mistakes in your initial design. The best way to find these mistakes is in a simulation environment. This tutorial is broken up into 2 stages:

1. Design of HDL
2. Simulation of HDL

Both of these steps are crucial for successful FPGA development. Sometimes FPGA designers who are pressed for time will try to skip step two, the simulation of their code. However this is an extremely important step! Without proper simulation you will be forced to debug your code on hardware which can be a very difficult and time consuming endeavour.

Rugrats munchin land pc. Project Requirements:

Design HDL code that will blink an LED at a specified frequency of 100 Hz, 50 Hz, 10 Hz, or 1 Hz. For each of the blink frequencies, the LED will be set to 50% duty cycle (it will be on half the time). The LED frequency will be chosen via two switches which are inputs to the FPGA. There is an additional switch called LED_EN that needs to be ‘1’ to turn on the LED. The FPGA will be driven by a 25 MHz oscillator.

Let’s first draw the truth table for the frequency selector:

For this to work correctly there will be 4 inputs and 1 output. The signals will be:

For the design there are four counter processes that run concurrently. This means that they are all running at the exact same time. Their job is to keep track of the number of clock pulses seen for each of the different frequencies. Even if the switches are not selecting that particular frequency, the counters are still running! This is the beauty of Hardware Design and concurrency. Everything runs all the time! It can be challenging to understand this initially, but it is the core concept that you need to master.

The switches only serve to select which output to use. They create what is known as a multiplexer. A multiplexer or mux for short is a selector that will select one of a number of inputs to propagate or pass to the output. It is a combinatorial piece of logic, meaning that it does not require a clock to operate. Below is a block diagram of the design. Spend some time thinking about how you might implement this design. Try writing the code yourself. The way that I chose to do can be found below.

Vhdl Simulator Online

VHDL code for the design, tutorial_led_blink.vhd:

Verilog code for the design, tutorial_led_blink.v:

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8 To 1 Multiplexer Verilog