This article examines how we can use configuration constructs to create variants of a module or testbench without maintaining multiple versions of the file. We will also look at other use cases for configuration declarations in VHDL design. Configurations have been part of the VHDL standard since the first version of the language. But still,…
There are two ways to instantiate a module in VHDL: component instantiation and entity instantiation. Some people refer to the latter as direct instantiation. Entity instantiation didn’t exist in the first revisions VHDL, but it has been available since VHDL’93. This is the method that I recommend unless you have specific reasons to use component…
The generate statement in VHDL can automatically duplicate a block of code to closures with identical signals, processes, and instances. It’s a for loop for the architecture region that can create chained processes or module instances.
Radio-controlled (RC) model servos are tiny actuators typically used in hobbyist model planes, cars, and boats. They allow the operator to control the vehicle via a radio link remotely. Because RC models have been around for a long time, the de-facto standard interface is pulse-width modulation (PWM), rather than a digital scheme. Fortunately, it’s easy…
Most VHDL simulators use the Tool Command Language (Tcl) as their scripting language. When you type a command in the console of the simulator, you are using Tcl. Furthermore, you can create scripts with Tcl that run in the simulator and interact with your VHDL code. In this article, we will create a self-checking testbench…
How do you stop the VHDL simulator when the simulation is complete? There are several ways to do that. In this article, we will examine the most common ways to end a successful testbench run. The VHDL code presented here is universal, and it should work in any capable VHDL simulator. For the methods involving…
When you have worked with VHDL code written by many other FPGA engineers, you are bound to notice that there are two common ways to model an edge detector in VHDL. There’s the rising_edge(clk) statement, and there’s the old style clk’event and clk = ‘1’ method. The two if-statements do the same thing once the…
This tutorial shows how to install the Lattice iCEcube2 FPGA design software on Ubuntu 20.04. Instead of the Lattice Diamond Programmer, we will use the alternative programmer from Project IceStorm that works flawlessly on Ubuntu Linux. The Lattice iCEcube2 FPGA design software only works on Red Hat-based Linux distributions out of the box. Fortunately, we…
I’ve noticed that many of the gadgets that I’ve bought the last couple of years have shifted away from LED blinking to led breathing. Most electronic gizmos contain a status LED whose behavior gives away indications of what’s going on inside of the device. My electric toothbrush flashes an LED when it’s time to recharge…
Pulse-width modulation (PWM) is an efficient way to control analog electronics from purely digital FPGA pins. Instead of attempting to regulate the analog voltage, PWM rapidly switches on and off the supply current at full power to the analog device. This method gives us precise control over the moving average of energy provided to the…
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