How to use a Case-When statement in VHDL

How to use a Case-When statement in VHDL

The Case-When statement will cause the program to take one out of multiple different paths, depending on the value of a signal, variable, or expression. It’s a more elegant alternative to an If-Then-Elsif-Else statement with multiple Elsif’s. Other programming languages have similar constructs, using keywords such as a switch, case, or select. Among other things,…

How to create a concurrent statement in VHDL

How to create a concurrent statement in VHDL

A concurrent statement in VHDL is a signal assignment within the architecture, but outside of a normal process construct. The concurrent statement is also referred to as a concurrent assignment or concurrent process. When you create a concurrent statement, you are actually creating a process with certain, clearly defined characteristics. Concurrent statements are always equivalent…

How to use Signed and Unsigned in VHDL

How to use Signed and Unsigned in VHDL

The signed and unsigned types in VHDL are bit vectors, just like the std_logic_vector type. The difference is that while the std_logic_vector is great for implementing data buses, it’s useless for performing arithmetic operations. If you try to add any number to a std_logic_vector type, ModelSim will produce the compilation error: No feasible entries for…

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