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//
// 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/>.
//
module gpif_rd
(input gpif_clk, input gpif_rst,
output [15:0] gpif_data, input gpif_rd, input gpif_ep,
output reg gpif_empty_d, output reg gpif_empty_c,
output reg gpif_flush,
input sys_clk, input sys_rst,
input [18:0] data_i, input src_rdy_i, output dst_rdy_o,
input [18:0] resp_i, input resp_src_rdy_i, output resp_dst_rdy_o,
output [31:0] debug
);
wire [18:0] data_o; // occ bit indicates flush
wire [17:0] resp_o; // no occ bit
wire final_rdy_data, final_rdy_resp;
// 33/257 Bug Fix
reg [8:0] read_count;
always @(negedge gpif_clk)
if(gpif_rst)
read_count <= 0;
else if(gpif_rd)
read_count <= read_count + 1;
else
read_count <= 0;
// Data Path
wire [18:0] data_int;
wire src_rdy_int, dst_rdy_int;
fifo_2clock_cascade #(.WIDTH(19), .SIZE(4)) rd_fifo_2clk
(.wclk(sys_clk), .datain(data_i[18:0]), .src_rdy_i(src_rdy_i), .dst_rdy_o(dst_rdy_o), .space(),
.rclk(~gpif_clk), .dataout(data_int), .src_rdy_o(src_rdy_int), .dst_rdy_i(dst_rdy_int), .occupied(),
.arst(sys_rst));
reg [7:0] packet_count;
wire consume_data_line = gpif_rd & ~gpif_ep & ~read_count[8];
wire produce_eop = src_rdy_int & dst_rdy_int & data_int[17];
wire consume_sop = consume_data_line & final_rdy_data & data_o[16];
wire consume_eop = consume_data_line & final_rdy_data & data_o[17];
fifo_cascade #(.WIDTH(19), .SIZE(10)) rd_fifo
(.clk(~gpif_clk), .reset(gpif_rst), .clear(0),
.datain(data_int), .src_rdy_i(src_rdy_int), .dst_rdy_o(dst_rdy_int), .space(),
.dataout(data_o), .src_rdy_o(final_rdy_data), .dst_rdy_i(consume_data_line), .occupied());
always @(negedge gpif_clk)
if(gpif_rst)
packet_count <= 0;
else
if(produce_eop & ~consume_sop)
packet_count <= packet_count + 1;
else if(consume_sop & ~produce_eop)
packet_count <= packet_count - 1;
always @(negedge gpif_clk)
if(gpif_rst)
gpif_empty_d <= 1;
else
gpif_empty_d <= ~|packet_count;
// Use occ bit to signal a gpif flush
always @(negedge gpif_clk)
if(gpif_rst)
gpif_flush <= 0;
else if(consume_eop & data_o[18])
gpif_flush <= ~gpif_flush;
// Response Path
wire [15:0] resp_fifolevel;
wire consume_resp_line = gpif_rd & gpif_ep & ~read_count[4];
fifo_2clock_cascade #(.WIDTH(18), .SIZE(4)) resp_fifo_2clk
(.wclk(sys_clk), .datain(resp_i[17:0]), .src_rdy_i(resp_src_rdy_i), .dst_rdy_o(resp_dst_rdy_o), .space(),
.rclk(~gpif_clk), .dataout(resp_o),
.src_rdy_o(final_rdy_resp), .dst_rdy_i(consume_resp_line), .occupied(resp_fifolevel),
.arst(sys_rst));
// FIXME -- handle short packets
always @(negedge gpif_clk)
if(gpif_rst)
gpif_empty_c <= 1;
else
gpif_empty_c <= resp_fifolevel < 16;
// Output Mux
assign gpif_data = gpif_ep ? resp_o[15:0] : data_o[15:0];
assign debug = { { 16'd0 },
{ data_int[17:16], data_o[17:16], packet_count[3:0] },
{ consume_sop, consume_eop, final_rdy_data, data_o[18], consume_data_line, consume_resp_line, src_rdy_int, dst_rdy_int} };
endmodule // gpif_rd
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