Reorganize repository

Signed-off-by: Alex Forencich <alex@alexforencich.com>

src/axis/rtl/taxi_axis_cobs_encode.sv

@@ -0,0 +1,469 @@
+// SPDX-License-Identifier: CERN-OHL-S-2.0
+/*
+
+Copyright (c) 2016-2025 FPGA Ninja, LLC
+
+Authors:
+- Alex Forencich
+
+*/
+
+`resetall
+`timescale 1ns / 1ps
+`default_nettype none
+
+/*
+ * AXI4-Stream consistent overhead byte stuffing (COBS) encoder
+ */
+module taxi_axis_cobs_encode #
+(
+    // append zero for in band framing
+    parameter logic APPEND_ZERO = 1'b1
+)
+(
+    input  wire logic  clk,
+    input  wire logic  rst,
+
+    /*
+     * AXI4-Stream input (sink)
+     */
+    taxi_axis_if.snk   s_axis,
+
+    /*
+     * AXI4-Stream output (source)
+     */
+    taxi_axis_if.src   m_axis
+);
+
+// check configuration
+if (m_axis.DATA_W != 8 || s_axis.DATA_W != 8)
+    $fatal(0, "Error: Interface DATA_W parameter mismatch (instance %m)");
+
+// state register
+localparam [1:0]
+    INPUT_STATE_IDLE = 2'd0,
+    INPUT_STATE_SEGMENT = 2'd1,
+    INPUT_STATE_FINAL_ZERO = 2'd2,
+    INPUT_STATE_APPEND_ZERO = 2'd3;
+
+logic [1:0] input_state_reg = INPUT_STATE_IDLE, input_state_next;
+
+localparam [0:0]
+    OUTPUT_STATE_IDLE = 1'd0,
+    OUTPUT_STATE_SEGMENT = 1'd1;
+
+logic [0:0] output_state_reg = OUTPUT_STATE_IDLE, output_state_next;
+
+logic [7:0] input_count_reg = 8'd0, input_count_next;
+logic [7:0] output_count_reg = 8'd0, output_count_next;
+logic fail_frame_reg = 1'b0, fail_frame_next;
+
+// internal datapath
+logic [7:0] m_axis_tdata_int;
+logic       m_axis_tvalid_int;
+logic       m_axis_tready_int_reg = 1'b0;
+logic       m_axis_tlast_int;
+logic       m_axis_tuser_int;
+wire        m_axis_tready_int_early;
+
+logic s_axis_tready_mask;
+
+taxi_axis_if #(.DATA_W(8), .USER_EN(1), .USER_W(1)) code_fifo_in(), code_fifo_out();
+taxi_axis_if #(.DATA_W(8)) data_fifo_in(), data_fifo_out();
+
+assign s_axis.tready = code_fifo_in.tready && data_fifo_in.tready && s_axis_tready_mask;
+
+taxi_axis_fifo #(
+    .DEPTH(256),
+    .FRAME_FIFO(0)
+)
+code_fifo_inst (
+    .clk(clk),
+    .rst(rst),
+
+    /*
+     * AXI4-Stream input (sink)
+     */
+    .s_axis(code_fifo_in),
+
+    /*
+     * AXI4-Stream output (source)
+     */
+    .m_axis(code_fifo_out),
+
+    /*
+     * Pause
+     */
+    .pause_req(),
+    .pause_ack(),
+
+    /*
+     * Status
+     */
+    .status_depth(),
+    .status_depth_commit(),
+    .status_overflow(),
+    .status_bad_frame(),
+    .status_good_frame()
+);
+
+taxi_axis_fifo #(
+    .DEPTH(256),
+    .FRAME_FIFO(0)
+)
+data_fifo_inst (
+    .clk(clk),
+    .rst(rst),
+
+    /*
+     * AXI4-Stream input (sink)
+     */
+    .s_axis(data_fifo_in),
+
+    /*
+     * AXI4-Stream output (source)
+     */
+    .m_axis(data_fifo_out),
+
+    /*
+     * Pause
+     */
+    .pause_req(),
+    .pause_ack(),
+
+    /*
+     * Status
+     */
+    .status_depth(),
+    .status_depth_commit(),
+    .status_overflow(),
+    .status_bad_frame(),
+    .status_good_frame()
+);
+
+always @* begin
+    input_state_next = INPUT_STATE_IDLE;
+
+    input_count_next = input_count_reg;
+
+    fail_frame_next = fail_frame_reg;
+
+    s_axis_tready_mask = 1'b0;
+
+    code_fifo_in.tdata = 8'd0;
+    code_fifo_in.tvalid = 1'b0;
+    code_fifo_in.tlast = 1'b0;
+    code_fifo_in.tuser = 1'b0;
+
+    data_fifo_in.tdata = s_axis.tdata;
+    data_fifo_in.tvalid = 1'b0;
+    data_fifo_in.tlast = 1'b0;
+    data_fifo_in.tuser = 1'b0;
+
+    case (input_state_reg)
+        INPUT_STATE_IDLE: begin
+            // idle state
+            s_axis_tready_mask = 1'b1;
+            fail_frame_next = 1'b0;
+
+            if (s_axis.tready && s_axis.tvalid) begin
+                // valid input data
+
+                if (s_axis.tdata == 8'd0 || (s_axis.tlast && s_axis.tuser)) begin
+                    // got a zero or propagated error, so store a zero code
+                    code_fifo_in.tdata = 8'd1;
+                    code_fifo_in.tvalid = 1'b1;
+                    if (s_axis.tlast) begin
+                        // last byte, so close out the frame
+                        fail_frame_next = s_axis.tuser;
+                        input_state_next = INPUT_STATE_FINAL_ZERO;
+                    end else begin
+                        // return to idle to await next segment
+                        input_state_next = INPUT_STATE_IDLE;
+                    end
+                end else begin
+                    // got something other than a zero, so store it and init the segment counter
+                    input_count_next = 8'd2;
+                    data_fifo_in.tdata = s_axis.tdata;
+                    data_fifo_in.tvalid = 1'b1;
+                    if (s_axis.tlast) begin
+                        // last byte, so store the code and close out the frame
+                        code_fifo_in.tdata = 8'd2;
+                        code_fifo_in.tvalid = 1'b1;
+                        if (APPEND_ZERO) begin
+                            // zero frame mode, need to add a zero code to end the frame
+                            input_state_next = INPUT_STATE_APPEND_ZERO;
+                        end else begin
+                            // normal frame mode, close out the frame
+                            data_fifo_in.tlast = 1'b1;
+                            input_state_next = INPUT_STATE_IDLE;
+                        end
+                    end else begin
+                        // await more segment data
+                        input_state_next = INPUT_STATE_SEGMENT;
+                    end
+                end
+            end else begin
+                input_state_next = INPUT_STATE_IDLE;
+            end
+        end
+        INPUT_STATE_SEGMENT: begin
+            // encode segment
+            s_axis_tready_mask = 1'b1;
+            fail_frame_next = 1'b0;
+
+            if (s_axis.tready && s_axis.tvalid) begin
+                // valid input data
+
+                if (s_axis.tdata == 8'd0 || (s_axis.tlast && s_axis.tuser)) begin
+                    // got a zero or propagated error, so store the code
+                    code_fifo_in.tdata = input_count_reg;
+                    code_fifo_in.tvalid = 1'b1;
+                    if (s_axis.tlast) begin
+                        // last byte, so close out the frame
+                        fail_frame_next = s_axis.tuser;
+                        input_state_next = INPUT_STATE_FINAL_ZERO;
+                    end else begin
+                        // return to idle to await next segment
+                        input_state_next = INPUT_STATE_IDLE;
+                    end
+                end else begin
+                    // got something other than a zero, so store it and increment the segment counter
+                    input_count_next = input_count_reg+1;
+                    data_fifo_in.tdata = s_axis.tdata;
+                    data_fifo_in.tvalid = 1'b1;
+                    if (input_count_reg == 8'd254) begin
+                        // 254 bytes in frame, so dump and reset counter
+                        code_fifo_in.tdata = input_count_reg+1;
+                        code_fifo_in.tvalid = 1'b1;
+                        input_count_next = 8'd1;
+                    end
+                    if (s_axis.tlast) begin
+                        // last byte, so store the code and close out the frame
+                        code_fifo_in.tdata = input_count_reg+1;
+                        code_fifo_in.tvalid = 1'b1;
+                        if (APPEND_ZERO) begin
+                            // zero frame mode, need to add a zero code to end the frame
+                            input_state_next = INPUT_STATE_APPEND_ZERO;
+                        end else begin
+                            // normal frame mode, close out the frame
+                            data_fifo_in.tlast = 1'b1;
+                            input_state_next = INPUT_STATE_IDLE;
+                        end
+                    end else begin
+                        // await more segment data
+                        input_state_next = INPUT_STATE_SEGMENT;
+                    end
+                end
+            end else begin
+                input_state_next = INPUT_STATE_SEGMENT;
+            end
+        end
+        INPUT_STATE_FINAL_ZERO: begin
+            // final zero code required
+            s_axis_tready_mask = 1'b0;
+
+            if (code_fifo_in.tready) begin
+                // push a zero code and close out frame
+                if (fail_frame_reg) begin
+                    code_fifo_in.tdata = 8'd2;
+                    code_fifo_in.tuser = 1'b1;
+                end else begin
+                    code_fifo_in.tdata = 8'd1;
+                end
+                code_fifo_in.tvalid = 1'b1;
+                if (APPEND_ZERO) begin
+                    // zero frame mode, need to add a zero code to end the frame
+                    input_state_next = INPUT_STATE_APPEND_ZERO;
+                end else begin
+                    // normal frame mode, close out the frame
+                    code_fifo_in.tlast = 1'b1;
+                    fail_frame_next = 1'b0;
+                    input_state_next = INPUT_STATE_IDLE;
+                end
+            end else begin
+                input_state_next = INPUT_STATE_FINAL_ZERO;
+            end
+        end
+        INPUT_STATE_APPEND_ZERO: begin
+            // append zero for zero framing
+            s_axis_tready_mask = 1'b0;
+
+            if (code_fifo_in.tready) begin
+                // push frame termination code and close out frame
+                code_fifo_in.tdata = 8'd0;
+                code_fifo_in.tlast = 1'b1;
+                code_fifo_in.tuser = fail_frame_reg;
+                code_fifo_in.tvalid = 1'b1;
+                fail_frame_next = 1'b0;
+                input_state_next = INPUT_STATE_IDLE;
+            end else begin
+                input_state_next = INPUT_STATE_APPEND_ZERO;
+            end
+        end
+    endcase
+end
+
+always @* begin
+    output_state_next = OUTPUT_STATE_IDLE;
+
+    output_count_next = output_count_reg;
+
+    m_axis_tdata_int = 8'd0;
+    m_axis_tvalid_int = 1'b0;
+    m_axis_tlast_int = 1'b0;
+    m_axis_tuser_int = 1'b0;
+
+    code_fifo_out.tready = 1'b0;
+
+    data_fifo_out.tready = 1'b0;
+
+    case (output_state_reg)
+        OUTPUT_STATE_IDLE: begin
+            // idle state
+
+            if (m_axis_tready_int_reg && code_fifo_out.tvalid) begin
+                // transfer out code byte and load counter
+                m_axis_tdata_int = code_fifo_out.tdata;
+                m_axis_tlast_int = code_fifo_out.tlast;
+                m_axis_tuser_int = code_fifo_out.tuser && code_fifo_out.tlast;
+                output_count_next = code_fifo_out.tdata-1;
+                m_axis_tvalid_int = 1'b1;
+                code_fifo_out.tready = 1'b1;
+                if (code_fifo_out.tdata == 8'd0 || code_fifo_out.tdata == 8'd1 || code_fifo_out.tuser) begin
+                    // frame termination and zero codes will be followed by codes
+                    output_state_next = OUTPUT_STATE_IDLE;
+                end else begin
+                    // transfer out data
+                    output_state_next = OUTPUT_STATE_SEGMENT;
+                end
+            end else begin
+                output_state_next = OUTPUT_STATE_IDLE;
+            end
+        end
+        OUTPUT_STATE_SEGMENT: begin
+            // segment output
+
+            if (m_axis_tready_int_reg && data_fifo_out.tvalid) begin
+                // transfer out data byte and decrement counter
+                m_axis_tdata_int = data_fifo_out.tdata;
+                m_axis_tlast_int = data_fifo_out.tlast;
+                output_count_next = output_count_reg - 1;
+                m_axis_tvalid_int = 1'b1;
+                data_fifo_out.tready = 1'b1;
+                if (output_count_reg == 1) begin
+                    // done with segment, get a code byte next
+                    output_state_next = OUTPUT_STATE_IDLE;
+                end else begin
+                    // more data to transfer
+                    output_state_next = OUTPUT_STATE_SEGMENT;
+                end
+            end else begin
+                output_state_next = OUTPUT_STATE_SEGMENT;
+            end
+        end
+    endcase
+end
+
+always @(posedge clk) begin
+    input_state_reg <= input_state_next;
+    output_state_reg <= output_state_next;
+
+    input_count_reg <= input_count_next;
+    output_count_reg <= output_count_next;
+    fail_frame_reg <= fail_frame_next;
+
+    if (rst) begin
+        input_state_reg <= INPUT_STATE_IDLE;
+        output_state_reg <= OUTPUT_STATE_IDLE;
+    end
+end
+
+// output datapath logic
+reg [7:0] m_axis_tdata_reg = 8'd0;
+reg       m_axis_tvalid_reg = 1'b0, m_axis_tvalid_next;
+reg       m_axis_tlast_reg = 1'b0;
+reg       m_axis_tuser_reg = 1'b0;
+
+reg [7:0] temp_m_axis_tdata_reg = 8'd0;
+reg       temp_m_axis_tvalid_reg = 1'b0, temp_m_axis_tvalid_next;
+reg       temp_m_axis_tlast_reg = 1'b0;
+reg       temp_m_axis_tuser_reg = 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 = 1'b1;
+assign m_axis.tstrb = m_axis.tkeep;
+assign m_axis.tvalid = m_axis_tvalid_reg;
+assign m_axis.tlast = m_axis_tlast_reg;
+assign m_axis.tid = '0;
+assign m_axis.tdest = '0;
+assign m_axis.tuser = m_axis_tuser_reg;
+
+// 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_tlast_reg <= m_axis_tlast_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_tlast_reg <= temp_m_axis_tlast_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_tlast_reg <= m_axis_tlast_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