Enums in VHDL

Based on your provided Go code example and the target language VHDL, here is the translated code and explanation in Markdown format suitable for Hugo.

Enumerated types (enums) are a special case of sum types. An enum is a type that has a fixed number of possible values, each with a distinct name. In VHDL, enums can be directly defined using the enumerated type feature.

Our enum type ServerState is defined using the type keyword in VHDL.

-- Define the ServerState enumerated type
type ServerState is (StateIdle, StateConnected, StateError, StateRetrying);

The possible values for ServerState are defined within the type declaration.

By implementing a function to convert ServerState values to strings, we can print out or convert these values when needed.

-- Function to convert ServerState to string
function ServerStateToString (ss : ServerState) return string is
begin
    case ss is
        when StateIdle =>
            return "idle";
        when StateConnected =>
            return "connected";
        when StateError =>
            return "error";
        when StateRetrying =>
            return "retrying";
    end case;
end function;

Now, we’ll write the transition function, which emulates a state transition for a server. It takes the existing state and returns a new state.

-- Function to handle state transitions
function transition(s : ServerState) return ServerState is
begin
    case s is
        when StateIdle =>
            return StateConnected;
        when StateConnected | StateRetrying =>
            return StateIdle;
        when StateError =>
            return StateError;
        when others =>
            assert false report "unknown state: " & ServerStateToString(s);
            return StateError;  -- default case for safety
    end case;
end function;

To test our transition function, we can write a process in VHDL that simulates the state transitions and prints the results.

-- Test process for state transitions
process
    variable currentState : ServerState := StateIdle;
begin
    currentState := transition(currentState);
    report ServerStateToString(currentState);  -- should output "connected"

    currentState := transition(currentState);
    report ServerStateToString(currentState);  -- should output "idle"

    -- Add more tests as needed
    wait;
end process;

To run the VHDL code, you can use a VHDL simulator like GHDL. Here is an example of how to run the simulation.

$ ghdl -a yourfile.vhdl
$ ghdl -e your_entity
$ ghdl -r your_entity

This outputs the results of the state transitions:

connected
idle

Now that we have demonstrated basic enumerated types and state transitions in VHDL, let’s explore more about the language.

Interfaces in VHDL

Struct Embedding in VHDL

Learn X By Example

Title here

Enums in VHDL