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dp_packet_unmerge.vhd 6.65 KiB
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--
-- Copyright (C) 2012
-- ASTRON (Netherlands Institute for Radio Astronomy) <http://www.astron.nl/>
-- P.O.Box 2, 7990 AA Dwingeloo, The Netherlands
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation, either version 3 of the License, or
-- (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-- GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with this program. If not, see <http://www.gnu.org/licenses/>.
--
--------------------------------------------------------------------------------
-- Purpose: Unmerge each input packet into output packets of length g_pkt_len.
-- Description:
-- . The merged packet length of the snk_in input packets must be an integer
-- multiple of g_pkt_len. The number of output packets g_nof_pkt_max is only
-- used to determine the maximum supported pkt_cnt range. The actual number
-- of output packets has to be <= g_nof_pkt_max, and is determined by input
-- packet length / g_pkt_len. Hence the dp_packet_unmerge can dynamically
-- handle different sizes of input packets, provided that their length is an
-- integer multiple of g_pkt_len.
-- . The pkt_cnt is passed on as src_out.channel index.
-- . The g_bsn_increment sets the BSN increment for the unmerged output
-- packets relative to the BSN of the snk_in input packet. When
-- g_bsn_increment = 0, then all unmerged output packets get the same BSN as
-- the input packet.
-- . The input snk_in.err and snk_in.empty are valid at the snk_in.eop, but
-- that is too late to apply them to the unmerged packets. Therefor assume
-- that the snk_in.err and snk_in_eop are already valid at the snk_in.sop
-- and remain valid until the snk_in.eop. Hence these signals are then valid
-- when snk_in.valid = '1'. Use same snk_in.err and snk_in.empty value for
-- all unmerged packets.
--
-- _ _ _
-- snk_in.sop _____| |___________________________| |___________________________| |_
-- _ _
-- snk_in.eop _________________________________| |___________________________| |___
-- _ _ _ _ _ _ _
-- src_out.sop _____|0|_______|1|_______|2|_______|0|_______|1|_______|2|_______|0|_
-- _ _ _ _ _ _
-- src_out.eop _____________|0|_______|1|_______|2|_______|0|_______|1|_______|2|___
library IEEE,common_lib;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;
use common_lib.common_pkg.all;
use work.dp_stream_pkg.all;
entity dp_packet_unmerge is
generic (
g_nof_pkt_max : natural := 1; -- Maximum nof packets to unmerge each incoming packet to
g_pkt_len : natural := 1; -- Length of the unmerged packets
g_bsn_increment : natural := 0
);
port (
rst : in std_logic;
clk : in std_logic;
snk_out : out t_dp_siso;
snk_in : in t_dp_sosi;
src_in : in t_dp_siso;
src_out : out t_dp_sosi
);
end dp_packet_unmerge;
architecture rtl of dp_packet_unmerge is
type t_reg is record
pkt_cnt : natural range 0 to g_nof_pkt_max + 1;
val_cnt : natural range 0 to g_pkt_len + 1;
src_out : t_dp_sosi;
end record;
constant c_reg_rst : t_reg := (0, 0, c_dp_sosi_rst);
signal r : t_reg;
signal d : t_reg;
begin
-- Map t_reg outputs to entity outputs
snk_out <= src_in;
src_out <= r.src_out;
-- p_reg
r <= d when rising_edge(clk);
p_comb : process(rst, r, snk_in)
variable v : t_reg;
begin
-- Default
v := r;
-- Function
-- _ _ _
-- snk_in.sop __| |_______________| |_______________| |_______________|
-- _ _ _
-- snk_in.eop _________________| |_______________| |_______________| |_
-- _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
-- snk_in.valid __|
-- v.val_cnt 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
-- v.pkt_cnt 0 1 2 0 1 2 0 1 2
-- ______________ _______________ _______________ _
-- v.busy __| |_| |_| |_|
-- _ _ _ _ _ _ _ _ _
-- v.src_out.sop __|0|___|1|___|2|___|0|___|1|___|2|___|0|___|1|___|2|___|
-- _ _ _ _ _ _ _ _ _
-- v.src_out.eop _____|0|___|1|___|2|___|0|___|1|___|2|___|0|___|1|___|2|_
-- input valid counter
if snk_in.sop = '1' then
v.val_cnt := 0;
elsif snk_in.valid = '1' then
if r.val_cnt < g_pkt_len - 1 then
v.val_cnt := r.val_cnt + 1;
else
v.val_cnt := 0;
end if;
end if;
-- output packet counter
if snk_in.sop = '1' then
v.pkt_cnt := 0;
elsif snk_in.valid = '1' and v.val_cnt = 0 then
v.pkt_cnt := r.pkt_cnt + 1;
end if;
-- output packet bsn, sync, sop and eop
v.src_out := snk_in; -- passes on snk_in.sync, data, re, im
v.src_out.bsn := r.src_out.bsn;
v.src_out.channel := r.src_out.channel;
v.src_out.empty := r.src_out.empty; v.src_out.err := r.src_out.err;
v.src_out.sop := '0';
v.src_out.eop := '0';
-- . output sop, eop
if snk_in.valid = '1' then
if v.val_cnt = 0 then
v.src_out.sop := '1';
end if;
if v.val_cnt = g_pkt_len - 1 then
v.src_out.eop := '1';
end if;
end if;
-- . output bsn
if snk_in.sop = '1' then
v.src_out.bsn := snk_in.bsn;
elsif v.src_out.sop = '1' then
v.src_out.bsn := incr_uvec(r.src_out.bsn, g_bsn_increment);
end if;
-- . output channel
v.src_out.channel := TO_DP_CHANNEL(v.pkt_cnt);
-- . output err, empty. assume they are valid during entire input packet,
-- so not only at the snk_in.eop
if snk_in.valid = '1' then
v.src_out.empty := snk_in.empty;
v.src_out.err := snk_in.err;
end if;
-- Synchronous reset
if rst = '1' then
v := c_reg_rst;
end if;
d <= v;
end process;
end rtl;