diff options
Diffstat (limited to 'fpga/usrp2/fifo/packet_padder36.v')
| -rw-r--r-- | fpga/usrp2/fifo/packet_padder36.v | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/fpga/usrp2/fifo/packet_padder36.v b/fpga/usrp2/fifo/packet_padder36.v new file mode 100644 index 000000000..6ded38781 --- /dev/null +++ b/fpga/usrp2/fifo/packet_padder36.v @@ -0,0 +1,155 @@ +// +// Copyright 2011-2012 Ettus Research LLC +// +// 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/>. +// + +// The packet padder 36 for use with RX VITA stream output. +// Packet padder understands the concept of USB LUTs, +// and will forward packets through the interface, +// adding zero padding as needed to properly flush. +// The padder will never write a packet across a LUT boundary. +// When flushing, padder writes out zeros until the LUT boundary. +// Requires that the input line0 be a VITA header, and SOF set. +// Flush when the LUT is partially filled and timeout is reached, +// or when the LUT is partially filled and the DSP is inactive. + +module packet_padder36 +#( + parameter BASE = 0, + + //default is 16K LUT + parameter DEFAULT_LINES32 = 4096, + + //default about 1ms at 64MHz clock + parameter DEFAULT_IDLE_CYC = 65536 +) +( + input clk, input reset, + + //setting bus + input set_stb, input [7:0] set_addr, input [31:0] set_data, + + //input interface + input [35:0] data_i, + input src_rdy_i, + output dst_rdy_o, + + //output interface + output [35:0] data_o, + output src_rdy_o, + input dst_rdy_i, + + input always_flush +); + + wire lut_lines_changed; + wire [15:0] max_lut_lines32; + setting_reg #(.my_addr(BASE+0),.width(16),.at_reset(DEFAULT_LINES32)) sr_num_lines( + .clk(clk),.rst(reset),.strobe(set_stb),.addr(set_addr),.in(set_data), + .out(max_lut_lines32),.changed(lut_lines_changed)); + + wire idle_cyc_changed; + wire [17:0] idle_flush_cycles; + setting_reg #(.my_addr(BASE+1),.width(18),.at_reset(DEFAULT_IDLE_CYC)) sr_flush_cyc( + .clk(clk),.rst(reset),.strobe(set_stb),.addr(set_addr),.in(set_data), + .out(idle_flush_cycles),.changed(idle_cyc_changed)); + + //state machine definitions + localparam STATE_READ_HDR = 0; + localparam STATE_WRITE_HDR = 1; + localparam STATE_FORWARD = 2; + localparam STATE_WRITE_PAD = 3; + reg [1:0] state; + + //keep track of the outgoing lines + reg [15:0] line_count; + wire line_count_done = line_count == 1; + wire lut_is_empty = line_count == max_lut_lines32; + always @(posedge clk) begin + if (reset || lut_lines_changed) begin + line_count <= max_lut_lines32; + end + else if (src_rdy_o && dst_rdy_i) begin + line_count <= (line_count_done)? max_lut_lines32 : line_count - 1; + end + end + + //count the number of cycles since RX data so we can force a flush + reg [17:0] non_rx_cycles; + wire idle_timeout = (non_rx_cycles == idle_flush_cycles); + always @(posedge clk) begin + if(reset || state != STATE_READ_HDR || idle_cyc_changed) begin + non_rx_cycles <= 0; + end + else if (~idle_timeout) begin + non_rx_cycles <= non_rx_cycles + 1; + end + end + + //flush when we have written data to a LUT and either idle or non active DSP + wire force_flush = ~lut_is_empty && (idle_timeout || always_flush); + + //the padding state machine + reg [31:0] vita_hdr; + reg has_vita_hdr; + always @(posedge clk) begin + if (reset) begin + state <= STATE_READ_HDR; + end + else case(state) + + STATE_READ_HDR: begin + if (src_rdy_i && dst_rdy_o && data_i[32]) begin + vita_hdr <= data_i[31:0]; + has_vita_hdr <= 1; + state <= (data_i[15:0] > line_count)? STATE_WRITE_PAD : STATE_WRITE_HDR; + end + else if (force_flush) begin + has_vita_hdr <= 0; + state <= STATE_WRITE_PAD; + end + end + + STATE_WRITE_HDR: begin + if (src_rdy_o && dst_rdy_i) begin + state <= STATE_FORWARD; + end + end + + STATE_FORWARD: begin + if (src_rdy_i && dst_rdy_o && data_i[33]) begin + state <= STATE_READ_HDR; + end + end + + STATE_WRITE_PAD: begin + if (src_rdy_o && dst_rdy_i && line_count_done) begin + state <= (has_vita_hdr)? STATE_WRITE_HDR : STATE_READ_HDR; + end + end + + endcase //state + end + + //assign outgoing signals + assign dst_rdy_o = (state == STATE_READ_HDR)? 1 : ((state == STATE_FORWARD)? dst_rdy_i : 0); + assign src_rdy_o = (state == STATE_WRITE_HDR || state == STATE_WRITE_PAD)? 1 : ((state == STATE_FORWARD )? src_rdy_i : 0); + assign data_o = (state == STATE_WRITE_HDR)? {4'b0001, vita_hdr} : ((state == STATE_FORWARD)? data_i : 0); + +endmodule // packet_padder36 + + + + |