There are controversies in the VHDL community about how you can and shouldn’t use subprograms. Some say you should avoid using functions or procedures in synthesizable (RTL) code.
While there are debatable subjective reasons to restrict the use of subprograms, many of these beliefs stem from myths or misconceptions. Therefore, I’m writing this article to give you clarity and understanding of subprograms so you can decide for yourself.
The ready/valid hardware data transfer protocol is simple and ingenious, providing flow control with only two control signals. The rules are straightforward: data transfer only happens when both ready and valid are ‘1’ during the same clock cycle.
A binary operator is an operator that takes exactly two arguments. Examples of such are addition or multiplication and, of course, the familiar Boolean logical operators we use in VHDL: and, or nand nor xor and xnor.
VHDL groups operators into classes with different precedence levels. Operators are evaluated according to their classes, starting with the highest level. Operators of the same class don’t have any predefined priority. Instead, they are evaluated left-to-right in the order they appear in the code.
The previously discussed filter describes a general-purpose device that can fit in many applications but is not necessarily the optimal solution. This is where application-specific FIR structures come in. Therefore, this post aims to present some of the more popular filter structures used in specialized applications.
As an FPGA designer, you have the freedom to implement the (finite impulse response) FIR filter either parallel or in series. Read the article to find out how to implement a FIR filter using VHDL!
Finite Impulse Response (FIR) and Infinite Impulse Response (IIR) are the two types of digital filters you’re most likely to use in FPGAs. This article discusses the implementation of the filters seen from the eyes of a hardware developer.
The ‘stable and ‘quiet attributes are predefined in the VHDL standard and work on signal objects. We can use these special features in simulation to check that a signal’s value remains untouched for a given period.
A latch is a logic element that can sample and hold a binary value, much like a flip-flop (register). But unlike a flip-flop, which is edge-triggered, the latch is level-triggered.
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, many FPGA designers never use them, perhaps because few people understand how configurations work.
I find that unfortunate because it’s really not that complicated.
