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// -*- verilog -*-
//
// USRP - Universal Software Radio Peripheral
//
// Copyright (C) 2003 Matt Ettus
//
// 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 2 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, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Boston, MA 02110-1301 USA
//
// Interface to Cypress FX2 bus
// A packet is 512 Bytes. Each fifo line is 2 bytes
// Fifo has 1024 or 2048 lines
module tx_buffer
( input usbclk,
input bus_reset, // Used here for the 257-Hack to fix the FX2 bug
input reset, // standard DSP-side reset
input [15:0] usbdata,
input wire WR,
output wire have_space,
output reg tx_underrun,
input wire [3:0] channels,
output reg [15:0] tx_i_0,
output reg [15:0] tx_q_0,
output reg [15:0] tx_i_1,
output reg [15:0] tx_q_1,
output reg [15:0] tx_i_2,
output reg [15:0] tx_q_2,
output reg [15:0] tx_i_3,
output reg [15:0] tx_q_3,
input txclk,
input txstrobe,
input clear_status,
output wire tx_empty,
output [11:0] debugbus
);
wire [11:0] txfifolevel;
reg [8:0] write_count;
wire tx_full;
wire [15:0] fifodata;
wire rdreq;
reg [3:0] load_next;
// DAC Side of FIFO
assign rdreq = ((load_next != channels) & !tx_empty);
always @(posedge txclk)
if(reset)
begin
{tx_i_0,tx_q_0,tx_i_1,tx_q_1,tx_i_2,tx_q_2,tx_i_3,tx_q_3}
<= #1 128'h0;
load_next <= #1 4'd0;
end
else
if((load_next != channels) & !tx_empty)
begin
load_next <= #1 load_next + 4'd1;
case(load_next)
4'd0 : tx_i_0 <= #1 fifodata;
4'd1 : tx_q_0 <= #1 fifodata;
4'd2 : tx_i_1 <= #1 fifodata;
4'd3 : tx_q_1 <= #1 fifodata;
4'd4 : tx_i_2 <= #1 fifodata;
4'd5 : tx_q_2 <= #1 fifodata;
4'd6 : tx_i_3 <= #1 fifodata;
4'd7 : tx_q_3 <= #1 fifodata;
endcase // case(load_next)
end // if ((load_next != channels) & !tx_empty)
else if(txstrobe & (load_next == channels))
begin
load_next <= #1 4'd0;
end
// USB Side of FIFO
assign have_space = (txfifolevel <= (4095-256));
always @(posedge usbclk)
if(bus_reset) // Use bus reset because this is on usbclk
write_count <= #1 0;
else if(WR & ~write_count[8])
write_count <= #1 write_count + 9'd1;
else
write_count <= #1 WR ? write_count : 9'b0;
// Detect Underruns
always @(posedge txclk)
if(reset)
tx_underrun <= 1'b0;
else if(txstrobe & (load_next != channels))
tx_underrun <= 1'b1;
else if(clear_status)
tx_underrun <= 1'b0;
// FIFO
fifo_4k txfifo
( .data ( usbdata ),
.wrreq ( WR & ~write_count[8] ),
.wrclk ( usbclk ),
.q ( fifodata ),
.rdreq ( rdreq ),
.rdclk ( txclk ),
.aclr ( reset ), // asynch, so we can use either
.rdempty ( tx_empty ),
.rdusedw ( ),
.wrfull ( tx_full ),
.wrusedw ( txfifolevel )
);
// Debugging Aids
assign debugbus[0] = WR;
assign debugbus[1] = have_space;
assign debugbus[2] = tx_empty;
assign debugbus[3] = tx_full;
assign debugbus[4] = tx_underrun;
assign debugbus[5] = write_count[8];
assign debugbus[6] = txstrobe;
assign debugbus[7] = rdreq;
assign debugbus[11:8] = load_next;
endmodule // tx_buffer
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