diff options
Diffstat (limited to 'fpga/usrp2/simple_gemac/ethtx_realign.v')
-rw-r--r-- | fpga/usrp2/simple_gemac/ethtx_realign.v | 94 |
1 files changed, 94 insertions, 0 deletions
diff --git a/fpga/usrp2/simple_gemac/ethtx_realign.v b/fpga/usrp2/simple_gemac/ethtx_realign.v new file mode 100644 index 000000000..236b2d4e1 --- /dev/null +++ b/fpga/usrp2/simple_gemac/ethtx_realign.v @@ -0,0 +1,94 @@ +// +// Copyright 2011 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/>. +// + + +//////////////////////////////////////////////////////////////////////// +// Ethernet TX - Realign +// +// - removes a 2-byte pad from the front a fifo36 stream +// - occupancy is preserved +// + +module ethtx_realign + (input clk, input reset, input clear, + input [35:0] datain, input src_rdy_i, output dst_rdy_o, + output [35:0] dataout, output src_rdy_o, input dst_rdy_i); + + reg [1:0] state; + reg [15:0] held; + reg [1:0] held_occ; + reg held_sof; + + wire xfer_in = src_rdy_i & dst_rdy_o; + wire xfer_out = src_rdy_o & dst_rdy_i; + + wire sof_in = datain[32]; + wire eof_in = datain[33]; + wire [1:0] occ_in = datain[35:34]; + wire occ_low = occ_in[1] ^ occ_in[0]; //occ is 1 or 2 + + always @(posedge clk) + if(reset | clear) + begin + held <= 0; + held_occ <= 0; + held_sof <= 0; + end + else if(xfer_in) + begin + held <= datain[15:0]; + held_occ <= occ_in; + held_sof <= sof_in; + end + + localparam RE_IDLE = 0; + localparam RE_HELD = 1; + localparam RE_DONE = 2; + + always @(posedge clk) + if(reset | clear) + state <= RE_IDLE; + else + case(state) + RE_IDLE : + if(xfer_in & eof_in) + state <= RE_DONE; + else if(xfer_in & sof_in) + state <= RE_HELD; + + RE_HELD : + if(xfer_in & xfer_out & eof_in) + if(occ_low) + state <= RE_IDLE; + else + state <= RE_DONE; + + RE_DONE : + if(xfer_out) + state <= RE_IDLE; + + endcase // case (state) + + wire sof_out = held_sof; + wire eof_out = (state == RE_HELD)? (eof_in & occ_low) : (state == RE_DONE); + wire [1:0] occ_out = ((state == RE_DONE)? held_occ : occ_in) ^ 2'b10; //(occ + 2)%4 + + assign dataout = {occ_out,eof_out,sof_out,held,datain[31:16]}; + assign src_rdy_o = (state == RE_HELD)? src_rdy_i : (state == RE_DONE); + assign dst_rdy_o = (state == RE_HELD)? dst_rdy_i : (state == RE_IDLE); + +endmodule // ethtx_realign |