vhdl/lib/emac/src/piso.vhd

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.NUMERIC_STD.ALL;
use std.textio.all; --  Imports the standard textio package.

use work.utils_pkg.all; --  Imports the standard textio package.

ENTITY piso IS
	Generic
	(
		data_width_in	: natural := 32;
		data_width_out	: natural := 8;
		msb_first		: boolean := false
	);
	Port
	(
		rst			: in  STD_LOGIC;
		clk			: in  STD_LOGIC;
		din_vld		: in  STD_LOGIC;
		din_rdy		: out STD_LOGIC;
		din_be		: in  unsigned(data_width_in/data_width_out-1 downto 0);
		din			: in  unsigned(data_width_in-1 downto 0);
		dout_vld	: out STD_LOGIC;
		dout_en		: in  STD_LOGIC;
		dout		: out unsigned(data_width_out-1 downto 0)
		
	);
END piso;

ARCHITECTURE behavior OF piso IS

	constant num_shifts		: natural := data_width_in/data_width_out;
	signal pre_fin			: STD_LOGIC;
	signal rdy				: STD_LOGIC;
	signal shift_cnt_pipe	: unsigned(num_shifts-1 downto 0);
	signal shift_pipe		: unsigned(data_width_in-1 downto 0);
	signal vld_pipe			: unsigned(num_shifts-1 downto 0);
	signal din_reg			: unsigned(data_width_in-1 downto 0);
	signal din_be_reg		: unsigned(num_shifts-1 downto 0);
	signal din_vld_reg		: STD_LOGIC;
	
--------------------------------------------------------------------------
begin

	pre_fin		<= shift_cnt_pipe(shift_cnt_pipe'left-1);
	din_rdy		<= rdy;
	dout_vld	<= vld_pipe(vld_pipe'left) when msb_first else vld_pipe(0);
	dout		<= 		shift_pipe(shift_pipe'left downto shift_pipe'left-data_width_out+1) when msb_first
				else	shift_pipe(data_width_out-1 downto 0);

--------------------------------------------------------------------------
process(clk)
begin
	if rising_edge(clk) then
		if rst = '1' then
			rdy			<= '0';
		elsif pre_fin = '1' and rdy = '0' then
			rdy		<= '1';
		elsif din_vld = '1' then
			rdy			<= '0';
		end if;
	end if;
end process;

process(clk)
begin
	if rising_edge(clk) then
		if rst = '1' then
			din_vld_reg	<= '0';
		elsif (pre_fin = '1' and dout_en = '1') or din_vld_reg = '0' then
			din_vld_reg	<= din_vld;
		end if;
	end if;
end process;

process(clk)
begin
	if rising_edge(clk) then
		if din_vld = '1' and rdy = '1' then
			din_reg		<= din;
			din_be_reg	<= din_be;
		end if;
	end if;
end process;

process(clk)
begin
	if rising_edge(clk) then
		if rst = '1' then
			shift_cnt_pipe	<= (others => '1');
		elsif (din_vld = '1' and din_vld_reg = '0') then
			shift_cnt_pipe	<= (others => '0');
		elsif dout_en = '1' then
			if (pre_fin = '1' and din_vld_reg = '1') then
				shift_cnt_pipe	<= (others => '0');
			else
				shift_cnt_pipe	<= shift_cnt_pipe(shift_cnt_pipe'left-1 downto 0)  & '1';
			end if;
		end if;
	end if;
end process;

--------------------------------------------------------------------------
process(clk)
begin
	if rising_edge(clk) then
		if dout_en = '1' then
			if pre_fin = '1' and din_vld_reg = '1' then
				shift_pipe		<= din_reg;
			else	
				if (msb_first) then
					shift_pipe		<= shift_pipe(shift_pipe'left-data_width_out downto 0) & (data_width_out-1 downto 0 => '0');
				else
					shift_pipe		<= (data_width_out-1 downto 0 => '0') & shift_pipe(shift_pipe'left downto data_width_out);
				end if;
			end if;
		end if;
	end if;
end process;

--------------------------------------------------------------------------
process(clk)
begin
	if rising_edge(clk) then
		if rst = '1' then
			vld_pipe	<= (others => '0');
		elsif dout_en = '1' then
			if pre_fin = '1' and din_vld_reg = '1' then
				vld_pipe		<= din_be_reg;
			else
				if (msb_first) then
					vld_pipe		<= vld_pipe(vld_pipe'left-1 downto 0) & '0';
				else
					vld_pipe		<= '0' & vld_pipe(vld_pipe'left downto 1);
				end if;
			end if;
		end if;
	end if;
end process;

--------------------------------------------------------------------------
end behavior;