Converting the image file to a bitmap format makes for the easiest way to read a picture using VHDL. Support for the BMP raster graphics image file format is built into the Microsoft Windows operating system. That makes BMP a suitable image format for storing photos for use in VHDL testbenches.
In this article, you will learn how to read a binary image file like BMP and store the data in dynamic memory in the simulator.
Reading signal values from file is an alternative way of generating stimuli for the device on test (DUT). The testbench sequence and timing is hard-coded in a stimulus file that is read by the VHDL testbench, line by line. This allows you to easily change the pattern of the waveform that you want to feed to the test object.
Sometimes you have a very specific test pattern or sequence of events that you want to put your DUT through.
A convenient way to populate block RAM with initial values is to read binary or hexadecimal literals from an ASCII file. This is also a good way to create a ROM (read-only memory) in VHDL. After all, RAM and ROM are the same thing in FPGAs, ROM is a RAM that you only read from.
The examples throughout this article will assume that the following constants and RAM type have been declared at the start of the declarative region of the VHDL file.
I was a little annoyed by the peculiarities of the AXI interface the first time I had to create logic to interface an AXI module. Instead of the regular busy/valid, full/valid, or empty/valid control signals, the AXI interface uses two control signals named “ready” and “valid”. My frustration soon changed to awe.
The AXI interface has built-in flow control without using additional control signals. The rules are easy enough to understand, but there are a few pitfalls one has to account for when implementing the AXI interface on an FPGA.
I know that I have googled this at least a hundred times throughout my career as an FPGA engineer; how to check if all bits in a std_logic_vector signal are ‘0’ or ‘1’. Of course, you know a few ways to do it already, but you want to find the most elegant code that will work with vectors of any length. Right?
Let’s have a look at the best methods for checking that all the bits in a vector are set or unset.
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 course is intended for the developer who has knowledge of other programming languages, but is new to VHDL and FPGAs.
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 packages for creating constrained random testbenches. We are particularly interested in the RandomPkg and CoveragePck, which we will be using in this article.
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 interface do you need? Are you limited by resources? Should it be resilient to over-read and overwrite? Is latency acceptable?
FPGA engineers are in high demand throughout the world’s defense industry. Military technology has extreme requirements for reliability and efficiency, things that can be provided by an FPGA.
As an FPGA developer, you will always be working for companies with particular needs, because FPGA development is expensive and difficult. The arms industry has both the need and the money, and therefore employs a lot of FPGA designers.
Based on my master’s thesis,
Tcl is the programming language that goes hand in hand with VHDL. You may choose to learn Verilog instead of VHDL, but you will be exposed to Tcl no matter which HDL you decide to use. That is because most FPGA related programs, such as simulators and synthesis tools, use Tcl in their command shells.
Having a standardized scripting language for software tools is actually very clever. It enables you to transfer your scripting skills from one tool to the next.
