I’m excited to announce that the VHDL and FPGA course that I have been working on for the last six months is starting to become complete. The course is in beta at the moment, and I am planning on launching it for the first time this autumn. Who is the FPGA course for? The FPGA…
Constrained random verification is a testbench strategy that relies on generating pseudo-random transactions for the device under test (DUT). The goal is to reach functional coverage of a number of predefined events through random interaction with the DUT. Open Source VHDL Verification Methodology (OSVVM) is a free VHDL library which includes a number of convenient…
Circular buffers are popular constructs for creating queues in sequential programming languages, but they can also be implemented in hardware. In this article, we will create a ring buffer in VHDL to implement a FIFO in block RAM. There are many design decisions you will have to make when implementing a FIFO. What kind of…
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…
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…
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….
An impure function can read or write any signal within its scope, also those that are not on the parameter list. We say that the function has side effects. What we mean by “side effects” is that it is not guaranteed that the function will return the same value every time it is called with…
Functions are subprograms in VHDL which can be used for implementing frequently used algorithms. A function takes zero or more input values, and it always returns a value. In addition to the return value, what sets a function apart from a procedure, is that it cannot contain Wait-statements. This means that functions always consume zero…
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