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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 double_buffer
#(parameter BUF_SIZE = 9)
(input clk, input reset, input clear,
// Random access interface to RAM
input access_we,
input access_stb,
output access_ok,
input access_done,
input access_skip_read,
input [BUF_SIZE-1:0] access_adr,
output [BUF_SIZE-1:0] access_len,
input [35:0] access_dat_i,
output [35:0] access_dat_o,
// Write FIFO Interface
input [35:0] data_i,
input src_rdy_i,
output dst_rdy_o,
// Read FIFO Interface
output [35:0] data_o,
output src_rdy_o,
input dst_rdy_i
);
wire [35:0] data_o_0, data_o_1;
wire read, read_ok, read_ptr, read_done;
wire write, write_ok, write_ptr, write_done;
wire [BUF_SIZE-1:0] rw0_adr, rw1_adr;
reg [BUF_SIZE-1:0] read_adr, write_adr;
reg [BUF_SIZE-1:0] len0, len1;
assign data_o = read_ptr ? data_o_1 : data_o_0;
assign rw0_adr = (write_ok & ~write_ptr) ? write_adr : read_adr;
assign rw1_adr = (write_ok & write_ptr) ? write_adr : read_adr;
wire [35:0] access_dat_o_0, access_dat_o_1;
wire access_ptr;
assign access_dat_o = access_ptr? access_dat_o_1 : access_dat_o_0;
dbsm dbsm
(.clk(clk), .reset(reset), .clear(clear),
.write_ok(write_ok), .write_ptr(write_ptr), .write_done(write_done),
.access_ok(access_ok), .access_ptr(access_ptr), .access_done(access_done), .access_skip_read(access_skip_read),
.read_ok(read_ok), .read_ptr(read_ptr), .read_done(read_done));
// Port A for random access, Port B for FIFO read and write
ram_2port #(.DWIDTH(36),.AWIDTH(BUF_SIZE)) buffer0
(.clka(clk),.ena(access_stb & access_ok & (access_ptr == 0)),.wea(access_we),
.addra(access_adr),.dia(access_dat_i),.doa(access_dat_o_0),
.clkb(clk),.enb((read & read_ok & ~read_ptr)|(write & write_ok & ~write_ptr) ),.web(write&write_ok&~write_ptr),
.addrb(rw0_adr),.dib(data_i),.dob(data_o_0));
ram_2port #(.DWIDTH(36),.AWIDTH(BUF_SIZE)) buffer1
(.clka(clk),.ena(access_stb & access_ok & (access_ptr == 1)),.wea(access_we),
.addra(access_adr),.dia(access_dat_i),.doa(access_dat_o_1),
.clkb(clk),.enb((read & read_ok & read_ptr)|(write & write_ok & write_ptr) ),.web(write&write_ok&write_ptr),
.addrb(rw1_adr),.dib(data_i),.dob(data_o_1));
// Write into buffers
assign dst_rdy_o = write_ok;
assign write = src_rdy_i & write_ok;
assign write_done = write & data_i[33]; // done
always @(posedge clk)
if(reset | clear)
write_adr <= 0;
else
if(write_done)
begin
write_adr <= 0;
if(write_ptr)
len1 <= write_adr + 1;
else
len0 <= write_adr + 1;
end
else if(write)
write_adr <= write_adr + 1;
assign access_len = access_ptr ? len1 : len0;
reg [1:0] read_state;
localparam IDLE = 0;
localparam PRE_READ = 1;
localparam READING = 2;
always @(posedge clk)
if(reset | clear)
begin
read_state <= IDLE;
read_adr <= 0;
end
else
case(read_state)
IDLE :
begin
read_adr <= 0;
if(read_ok)
read_state <= PRE_READ;
end
PRE_READ :
begin
read_state <= READING;
read_adr <= 1;
end
READING :
if(dst_rdy_i)
begin
read_adr <= read_adr + 1;
if(data_o[33])
read_state <= IDLE;
end
endcase // case (read_state)
assign read = ~((read_state==READING)& ~dst_rdy_i);
assign read_done = data_o[33] & dst_rdy_i & src_rdy_o;
assign src_rdy_o = (read_state == READING);
endmodule // double_buffer
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