An interactive testbench is a simulator setup where input to the device under test (DUT) is provided by an operator while the testbench is running. Most often, this would mean you entering commands in the simulator console to provide the DUT with stimulus. While you should always create a self-checking testbench, an interactive testbench can…
A self-checking testbench is a VHDL program that verifies the correctness of the device under test (DUT) without relying on an operator to manually inspect the output. The self-checking testbench runs entirely on its own, and prints an “OK” or “Failed” message in the end. Every VHDL module should have an associated self-checking testbench. It’s…
As most hardware engineers, I started off my computer science career by learning a sequential programming language. The first language I learned at the University of Oslo was Java. While it’s not considered to be the most exciting language today, at the time, Java was at the pinnacle of its popularity. The engineers who built…
The VHDL Analysis and Standardization Group (VASG), has been working for quite some time on finishing the draft for the upcoming VHDL-2019 revision of the language. The ballot has been held, and a list of approved changes has emerged. What’s left before this becomes the latest revision of the VHDL language is for the draft…
The linked list is a dynamic data structure. A linked list can be used when the total number of elements is not known in advance. It grows and shrinks in memory, relative to the number of items it contains. Linked lists are most conveniently implemented using classes in an object-oriented programming language. VHDL has some…
VHDL includes few built-in types but offers several additional types through extension packages. Two of the most widely used types are std_logic and std_ulogic. The difference between them is that the former is resolved while the latter isn’t. Before we go on to investigate what it means that a type is resolved, let’s first look…
Delta cycles are non-time-consuming timesteps used by VHDL simulators for modeling events during execution of VHDL code. They are events that happen in zero simulation time after a preceding event. VHDL is a parallel programming language, while computers and CPUs work in a sequential manner. When a normal programming language is run, the CPU executes…
Most of us stick to a certain way of writing a state machine. Perhaps you type out the construct that you are most familiar with without giving much thought to the alternatives. Depending on the method that you were taught when learning VHDL, you may prefer one method to another. Over the years, I have…
Test your progress with this VHDL quiz after completing part 4 of the Basic VHDL Tutorial series!
It is possible to drive external signals from a procedure. As long as the signal is within the scope of the procedure, it can be accessed for reading or writing, even if it isn’t listed in the parameter list. Procedures that are declared in the declarative region of the architecture, cannot drive any external signals….
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