Select in VHDL

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity SelectExample is
end SelectExample;

architecture Behavioral of SelectExample is
    -- Declare signals for simulation
    signal c1, c2 : std_logic := '0';
    signal msg1, msg2 : string(1 to 3);
begin
    -- Simulate channel 1
    process
    begin
        wait for 1 sec;
        c1 <= '1';
        msg1 <= "one";
        wait;
    end process;

    -- Simulate channel 2
    process
    begin
        wait for 2 sec;
        c2 <= '1';
        msg2 <= "two";
        wait;
    end process;

    -- Main process to select between channels
    process
    begin
        for i in 1 to 2 loop
            wait on c1, c2;
            if c1 = '1' then
                report "received " & msg1;
                c1 <= '0';
            elsif c2 = '1' then
                report "received " & msg2;
                c2 <= '0';
            end if;
        end loop;
        wait;
    end process;
end Behavioral;

This VHDL code simulates the behavior of the original Select example. Here’s an explanation of the translation:

In VHDL, we don’t have direct equivalents for goroutines and channels. Instead, we use concurrent processes to simulate parallel execution and signals to communicate between processes.

We define two signals c1 and c2 to represent the channels, and msg1 and msg2 to hold the messages.

Two separate processes simulate the behavior of the original goroutines:

• The first process waits for 1 second, then sets c1 to ‘1’ and msg1 to “one”.
• The second process waits for 2 seconds, then sets c2 to ‘1’ and msg2 to “two”.

The main process simulates the select statement:

• It uses a wait on c1, c2 statement to wait for either signal to change.
• When a signal changes, it checks which one changed and reports the corresponding message.
• This process loops twice to match the original example.

To simulate this VHDL code, you would use a VHDL simulator. The simulation would run for about 2 seconds, and you would see output similar to:

# At 1 sec: received one
# At 2 sec: received two

Note that VHDL is typically used for hardware description and simulation, so this example is more of a conceptual translation rather than a practical VHDL application. In real VHDL designs, you would typically be describing actual hardware behavior rather than simulating software-like constructs.