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axis_rate_limit.v
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axis_rate_limit.v
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/*
Copyright (c) 2014-2018 Alex Forencich
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
// Language: Verilog 2001
`resetall
`timescale 1ns / 1ps
`default_nettype none
/*
* AXI4-Stream rate limiter
*/
module axis_rate_limit #
(
// Width of AXI stream interfaces in bits
parameter DATA_WIDTH = 8,
// Propagate tkeep signal
// If disabled, tkeep assumed to be 1'b1
parameter KEEP_ENABLE = (DATA_WIDTH>8),
// tkeep signal width (words per cycle)
parameter KEEP_WIDTH = ((DATA_WIDTH+7)/8),
// Propagate tlast signal
parameter LAST_ENABLE = 1,
// Propagate tid signal
parameter ID_ENABLE = 0,
// tid signal width
parameter ID_WIDTH = 8,
// Propagate tdest signal
parameter DEST_ENABLE = 0,
// tdest signal width
parameter DEST_WIDTH = 8,
// Propagate tuser signal
parameter USER_ENABLE = 1,
// tuser signal width
parameter USER_WIDTH = 1
)
(
input wire clk,
input wire rst,
/*
* AXI input
*/
input wire [DATA_WIDTH-1:0] s_axis_tdata,
input wire [KEEP_WIDTH-1:0] s_axis_tkeep,
input wire s_axis_tvalid,
output wire s_axis_tready,
input wire s_axis_tlast,
input wire [ID_WIDTH-1:0] s_axis_tid,
input wire [DEST_WIDTH-1:0] s_axis_tdest,
input wire [USER_WIDTH-1:0] s_axis_tuser,
/*
* AXI output
*/
output wire [DATA_WIDTH-1:0] m_axis_tdata,
output wire [KEEP_WIDTH-1:0] m_axis_tkeep,
output wire m_axis_tvalid,
input wire m_axis_tready,
output wire m_axis_tlast,
output wire [ID_WIDTH-1:0] m_axis_tid,
output wire [DEST_WIDTH-1:0] m_axis_tdest,
output wire [USER_WIDTH-1:0] m_axis_tuser,
/*
* Configuration
*/
input wire [7:0] rate_num,
input wire [7:0] rate_denom,
input wire rate_by_frame
);
// internal datapath
reg [DATA_WIDTH-1:0] m_axis_tdata_int;
reg [KEEP_WIDTH-1:0] m_axis_tkeep_int;
reg m_axis_tvalid_int;
reg m_axis_tready_int_reg = 1'b0;
reg m_axis_tlast_int;
reg [ID_WIDTH-1:0] m_axis_tid_int;
reg [DEST_WIDTH-1:0] m_axis_tdest_int;
reg [USER_WIDTH-1:0] m_axis_tuser_int;
wire m_axis_tready_int_early;
reg [23:0] acc_reg = 24'd0, acc_next;
reg pause;
reg frame_reg = 1'b0, frame_next;
reg s_axis_tready_reg = 1'b0, s_axis_tready_next;
assign s_axis_tready = s_axis_tready_reg;
always @* begin
acc_next = acc_reg;
pause = 1'b0;
frame_next = frame_reg;
if (acc_reg >= rate_num) begin
acc_next = acc_reg - rate_num;
end
if (s_axis_tready && s_axis_tvalid) begin
// read input
frame_next = !s_axis_tlast;
acc_next = acc_reg + (rate_denom - rate_num);
end
if (acc_next >= rate_num) begin
if (LAST_ENABLE && rate_by_frame) begin
pause = !frame_next;
end else begin
pause = 1'b1;
end
end
s_axis_tready_next = m_axis_tready_int_early && !pause;
m_axis_tdata_int = s_axis_tdata;
m_axis_tkeep_int = s_axis_tkeep;
m_axis_tvalid_int = s_axis_tvalid && s_axis_tready;
m_axis_tlast_int = s_axis_tlast;
m_axis_tid_int = s_axis_tid;
m_axis_tdest_int = s_axis_tdest;
m_axis_tuser_int = s_axis_tuser;
end
always @(posedge clk) begin
acc_reg <= acc_next;
frame_reg <= frame_next;
s_axis_tready_reg <= s_axis_tready_next;
if (rst) begin
acc_reg <= 24'd0;
frame_reg <= 1'b0;
s_axis_tready_reg <= 1'b0;
end
end
// output datapath logic
reg [DATA_WIDTH-1:0] m_axis_tdata_reg = {DATA_WIDTH{1'b0}};
reg [KEEP_WIDTH-1:0] m_axis_tkeep_reg = {KEEP_WIDTH{1'b0}};
reg m_axis_tvalid_reg = 1'b0, m_axis_tvalid_next;
reg m_axis_tlast_reg = 1'b0;
reg [ID_WIDTH-1:0] m_axis_tid_reg = {ID_WIDTH{1'b0}};
reg [DEST_WIDTH-1:0] m_axis_tdest_reg = {DEST_WIDTH{1'b0}};
reg [USER_WIDTH-1:0] m_axis_tuser_reg = {USER_WIDTH{1'b0}};
reg [DATA_WIDTH-1:0] temp_m_axis_tdata_reg = {DATA_WIDTH{1'b0}};
reg [KEEP_WIDTH-1:0] temp_m_axis_tkeep_reg = {KEEP_WIDTH{1'b0}};
reg temp_m_axis_tvalid_reg = 1'b0, temp_m_axis_tvalid_next;
reg temp_m_axis_tlast_reg = 1'b0;
reg [ID_WIDTH-1:0] temp_m_axis_tid_reg = {ID_WIDTH{1'b0}};
reg [DEST_WIDTH-1:0] temp_m_axis_tdest_reg = {DEST_WIDTH{1'b0}};
reg [USER_WIDTH-1:0] temp_m_axis_tuser_reg = {USER_WIDTH{1'b0}};
// datapath control
reg store_axis_int_to_output;
reg store_axis_int_to_temp;
reg store_axis_temp_to_output;
assign m_axis_tdata = m_axis_tdata_reg;
assign m_axis_tkeep = KEEP_ENABLE ? m_axis_tkeep_reg : {KEEP_WIDTH{1'b1}};
assign m_axis_tvalid = m_axis_tvalid_reg;
assign m_axis_tlast = LAST_ENABLE ? m_axis_tlast_reg : 1'b1;
assign m_axis_tid = ID_ENABLE ? m_axis_tid_reg : {ID_WIDTH{1'b0}};
assign m_axis_tdest = DEST_ENABLE ? m_axis_tdest_reg : {DEST_WIDTH{1'b0}};
assign m_axis_tuser = USER_ENABLE ? m_axis_tuser_reg : {USER_WIDTH{1'b0}};
// enable ready input next cycle if output is ready or the temp reg will not be filled on the next cycle (output reg empty or no input)
assign m_axis_tready_int_early = m_axis_tready || (!temp_m_axis_tvalid_reg && (!m_axis_tvalid_reg || !m_axis_tvalid_int));
always @* begin
// transfer sink ready state to source
m_axis_tvalid_next = m_axis_tvalid_reg;
temp_m_axis_tvalid_next = temp_m_axis_tvalid_reg;
store_axis_int_to_output = 1'b0;
store_axis_int_to_temp = 1'b0;
store_axis_temp_to_output = 1'b0;
if (m_axis_tready_int_reg) begin
// input is ready
if (m_axis_tready || !m_axis_tvalid_reg) begin
// output is ready or currently not valid, transfer data to output
m_axis_tvalid_next = m_axis_tvalid_int;
store_axis_int_to_output = 1'b1;
end else begin
// output is not ready, store input in temp
temp_m_axis_tvalid_next = m_axis_tvalid_int;
store_axis_int_to_temp = 1'b1;
end
end else if (m_axis_tready) begin
// input is not ready, but output is ready
m_axis_tvalid_next = temp_m_axis_tvalid_reg;
temp_m_axis_tvalid_next = 1'b0;
store_axis_temp_to_output = 1'b1;
end
end
always @(posedge clk) begin
m_axis_tvalid_reg <= m_axis_tvalid_next;
m_axis_tready_int_reg <= m_axis_tready_int_early;
temp_m_axis_tvalid_reg <= temp_m_axis_tvalid_next;
// datapath
if (store_axis_int_to_output) begin
m_axis_tdata_reg <= m_axis_tdata_int;
m_axis_tkeep_reg <= m_axis_tkeep_int;
m_axis_tlast_reg <= m_axis_tlast_int;
m_axis_tid_reg <= m_axis_tid_int;
m_axis_tdest_reg <= m_axis_tdest_int;
m_axis_tuser_reg <= m_axis_tuser_int;
end else if (store_axis_temp_to_output) begin
m_axis_tdata_reg <= temp_m_axis_tdata_reg;
m_axis_tkeep_reg <= temp_m_axis_tkeep_reg;
m_axis_tlast_reg <= temp_m_axis_tlast_reg;
m_axis_tid_reg <= temp_m_axis_tid_reg;
m_axis_tdest_reg <= temp_m_axis_tdest_reg;
m_axis_tuser_reg <= temp_m_axis_tuser_reg;
end
if (store_axis_int_to_temp) begin
temp_m_axis_tdata_reg <= m_axis_tdata_int;
temp_m_axis_tkeep_reg <= m_axis_tkeep_int;
temp_m_axis_tlast_reg <= m_axis_tlast_int;
temp_m_axis_tid_reg <= m_axis_tid_int;
temp_m_axis_tdest_reg <= m_axis_tdest_int;
temp_m_axis_tuser_reg <= m_axis_tuser_int;
end
if (rst) begin
m_axis_tvalid_reg <= 1'b0;
m_axis_tready_int_reg <= 1'b0;
temp_m_axis_tvalid_reg <= 1'b0;
end
end
endmodule
`resetall