N相クロックを作るその4 / rol (左回転)演算子を使う -

というわけでローテート演算子の存在を知ったのでrol演算子を使ってN相クロックを作る。最初からこうすべきであった。

VHDL_for_Quartus_Prime/one_hot_state_counter_ver2 at main · ti-nspire/VHDL_for_Quartus_Prime · GitHub

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity one_hot_state_counter is
    generic(
        NUM_PHASES: natural := 16
    );
    port(
        aclr_n: in std_logic;
        sclr_n: in std_logic;
        clk   : in std_logic;

        n_phase_clk: out std_logic_vector(NUM_PHASES-1 downto 0)
    );
end entity;

architecture rtl of one_hot_state_counter is
begin

    process(all)
        constant uns_1  : unsigned(NUM_PHASES-1 downto 0) := to_unsigned(1, NUM_PHASES);
        variable one_hot: unsigned(NUM_PHASES-1 downto 0) := uns_1;
    begin
        if aclr_n = '0' then -- asynchronous reset
            one_hot := uns_1;
        elsif rising_edge(clk) then
            if sclr_n = '0' then -- synchronous reset
                one_hot := uns_1;
            else -- when not reseting, synchronous rotate left.
                one_hot := one_hot rol 1;
            end if;
        end if;
        n_phase_clk <= std_logic_vector(one_hot);
    end process;

end architecture;