![]() Signals depend on if it’s combinational or sequential code to know when the signal takes the value of the assignment. Variables that are assigned immediately take the value of the assignment. ![]() Signals are assigned using the <= assignment symbol. ![]() Variables are assigned using the := assignment symbol.Signals are defined in the architecture before the begin statement. Variables need to be defined after the keyword process but before the keyword begin.Any variable that is created in one process cannot be used in another process, signals can be used in multiple processes though they can only be assigned in a single process.Variables can only be used inside processes, signals can be used inside or outside processes.If you need a refresher, try this page about VHDL variables. However the differences are more significant than this and must be clearly understood to know when to use which one. The most obvious difference is that variables use the := assignment symbol whereas signals use the <= assignment symbol. They can both be used to hold any type of data assigned to them. Variables and Signals in VHDL appears to be very similar. ![]()
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