+--
+-- * Counter - divider *
+--
+-- part of LXPWR motion control board (c) PiKRON Ltd
+-- idea by Pavel Pisa PiKRON Ltd <ppisa@pikron.com>
+--
+-- license: BSD
+--
+-- This file is used in "RPI PMS motor control" as frequency divider - divides by 6
+
+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
+
+entity cnt_div is
+ generic (
+ cnt_width_g : natural := 4
+ );
+ port
+ (
+ clk_i : in std_logic; --clk to divide
+ en_i : in std_logic; --enable bit?
+ reset_i : in std_logic; --asynch. reset
+ ratio_i : in std_logic_vector(cnt_width_g-1 downto 0);--initial value
+ q_out_o : out std_logic --generates puls when counter underflows
+ );
+end cnt_div;
+
+architecture behavioral of cnt_div is
+ signal cnt_val_s : natural range 0 to (2**cnt_width_g - 1); --counter value before DFF
+ signal cnt_val_r : natural range 0 to (2**cnt_width_g - 1); --counter value after DFF
+begin
+
+comb: process (reset_i, en_i, ratio_i, cnt_val_r)
+ begin
+ if reset_i = '1' then --reset detection
+ cnt_val_s <= to_integer(unsigned(ratio_i)); --set initial value
+ q_out_o <= '0'; --reset output
+ else
+ if en_i = '0' then --stop-state
+ cnt_val_s <= cnt_val_r; --hold the value
+ q_out_o <= '0'; --reset output
+ else
+ if cnt_val_r <= 1 then --counter underflows
+ cnt_val_s <= to_integer(unsigned(ratio_i)); --set initial value
+ q_out_o <= '1'; --set output
+ else
+ cnt_val_s <= cnt_val_r - 1; --decrement counter
+ q_out_o <= '0'; --reset output
+ end if;
+ end if;
+ end if;
+ end process;
+
+seq: process
+ begin
+ wait until clk_i'event and clk_i = '1';
+ cnt_val_r <= cnt_val_s;
+ end process;
+
+end behavioral;
+