Subversion Repositories dp_components

-------------------------------------------------------------------------------

--

-- Copyright 2020

-- ASTRON (Netherlands Institute for Radio Astronomy) <http://www.astron.nl/>

-- P.O.Box 2, 7990 AA Dwingeloo, The Netherlands

-- 

-- Licensed under the Apache License, Version 2.0 (the "License");

-- you may not use this file except in compliance with the License.

-- You may obtain a copy of the License at

-- 

--     http://www.apache.org/licenses/LICENSE-2.0

-- 

-- Unless required by applicable law or agreed to in writing, software

-- distributed under the License is distributed on an "AS IS" BASIS,

-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

-- See the License for the specific language governing permissions and

-- limitations under the License.

--

-------------------------------------------------------------------------------

LIBRARY IEEE, common_pkg_lib, dp_pkg_lib;

USE IEEE.std_logic_1164.ALL;

USE IEEE.numeric_std.ALL;

USE common_pkg_lib.common_pkg.ALL;

USE dp_pkg_lib.dp_stream_pkg.ALL;

-- Purpose:

--   Typically used in dp_latency_adapter.

-- Description:

--   Increase the output ready latency by g_incr_latency compared to the input

--   ready latency g_in_latency. Hence the output latency becomes g_in_latency

--   + g_incr_latency.

-- Remark:

-- . The SOSI data stream signals (i.e. data, empty, channel, err) are passed

--   on as wires.

-- . The out_sync, out_val, out_sop and out_eop are internally AND with the

--   delayed src_in.ready, this is only truely necessary if the input ready

--   latency is 0, but it does not harm to do it also when the input ready

--   latency > 0. However to easy achieving P&R timing it is better to not have

--   unnessary logic in the combinatorial path of out_sync, out_val, out_sop

--   and out_eop, therefore the AND with reg_val is only generated when

--   g_in_latency=0.

ENTITY dp_latency_increase IS

  GENERIC (

    g_in_latency   : NATURAL := 0;  -- >= 0

    g_incr_latency : NATURAL := 2   -- >= 0

  );

  PORT (

    rst          : IN  STD_LOGIC;

    clk          : IN  STD_LOGIC;

    -- ST sink

    snk_out      : OUT t_dp_siso;

    snk_in       : IN  t_dp_sosi;

    -- ST source

    src_in       : IN  t_dp_siso;

    src_out      : OUT t_dp_sosi

  );

END dp_latency_increase;

ARCHITECTURE rtl OF dp_latency_increase IS

  CONSTANT c_out_latency : NATURAL := g_in_latency + g_incr_latency;

  SIGNAL reg_ready : STD_LOGIC_VECTOR(c_out_latency DOWNTO 0);

  SIGNAL reg_val   : STD_LOGIC;

  SIGNAL i_snk_out : t_dp_siso := c_dp_siso_rdy;

BEGIN

  -- Use i_snk_out with defaults to force unused snk_out bits and fields to '0'

  snk_out <= i_snk_out;

  -- Support wires only for g_incr_latency=0

  no_latency : IF g_incr_latency=0 GENERATE

    i_snk_out <= src_in;  -- SISO

    src_out   <= snk_in;  -- SOSI

  END GENERATE no_latency;

  gen_latency : IF g_incr_latency>0 GENERATE

    -- SISO

    reg_ready(0) <= src_in.ready;  -- use reg_ready(0) to combinatorially store src_in.ready

    p_clk : PROCESS(rst, clk)

    BEGIN

      IF rst='1' THEN

        reg_ready(c_out_latency DOWNTO 1) <= (OTHERS=>'0');

      ELSIF rising_edge(clk) THEN

        reg_ready(c_out_latency DOWNTO 1) <= reg_ready(c_out_latency-1 DOWNTO 0);

      END IF;

    END PROCESS;

    i_snk_out.xon   <= src_in.xon;                 -- Pass on frame level flow control

    i_snk_out.ready <= reg_ready(g_incr_latency);  -- Adjust ready latency

    -- SOSI

    gen_out : IF g_in_latency/=0 GENERATE

      src_out <= snk_in;

    END GENERATE;

    gen_zero_out : IF g_in_latency=0 GENERATE

      reg_val <= reg_ready(c_out_latency);

      p_src_out : PROCESS(snk_in, reg_val)

      BEGIN

        src_out       <= snk_in;

        src_out.sync  <= snk_in.sync  AND reg_val;

        src_out.valid <= snk_in.valid AND reg_val;

        src_out.sop   <= snk_in.sop   AND reg_val;

        src_out.eop   <= snk_in.eop   AND reg_val;

      END PROCESS;

    END GENERATE;

  END GENERATE gen_latency;

END rtl;