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// FIFO Interface to the 2K buffer RAMs
// Read port is read-acknowledge
// FIXME do we want to be able to interleave reads and writes?
module buffer_int
#(parameter BUF_NUM = 0,
parameter BUF_SIZE = 9)
(// Control Interface
input clk,
input rst,
input [31:0] ctrl_word,
input go,
output done,
output error,
output idle,
// Buffer Interface
output en_o,
output we_o,
output reg [BUF_SIZE-1:0] addr_o,
output [31:0] dat_to_buf,
input [31:0] dat_from_buf,
// Write FIFO Interface
input [31:0] wr_data_i,
input [3:0] wr_flags_i,
input wr_ready_i,
output wr_ready_o,
// Read FIFO Interface
output [31:0] rd_data_o,
output [3:0] rd_flags_o,
output rd_ready_o,
input rd_ready_i
);
reg [31:0] ctrl_reg;
reg go_reg;
always @(posedge clk)
go_reg <= go;
always @(posedge clk)
if(rst)
ctrl_reg <= 0;
else
if(go & (ctrl_word[31:28] == BUF_NUM))
ctrl_reg <= ctrl_word;
wire [BUF_SIZE-1:0] firstline = ctrl_reg[BUF_SIZE-1:0];
wire [BUF_SIZE-1:0] lastline = ctrl_reg[2*BUF_SIZE-1:BUF_SIZE];
wire read = ctrl_reg[22];
wire write = ctrl_reg[23];
wire clear = ctrl_reg[24];
//wire [2:0] port = ctrl_reg[27:25]; // Ignored in this block
//wire [3:0] buff_num = ctrl_reg[31:28]; // Ignored here ?
localparam IDLE = 3'd0;
localparam PRE_READ = 3'd1;
localparam READING = 3'd2;
localparam WRITING = 3'd3;
localparam ERROR = 3'd4;
localparam DONE = 3'd5;
reg [2:0] state;
reg rd_sop, rd_eop;
wire wr_sop, wr_eop, wr_error;
reg [1:0] rd_occ;
wire [1:0] wr_occ;
always @(posedge clk)
if(rst)
begin
state <= IDLE;
rd_sop <= 0;
rd_eop <= 0;
rd_occ <= 0;
end
else
if(clear)
begin
state <= IDLE;
rd_sop <= 0;
rd_eop <= 0;
rd_occ <= 0;
end
else
case(state)
IDLE :
if(go_reg & read)
begin
addr_o <= firstline;
state <= PRE_READ;
end
else if(go_reg & write)
begin
addr_o <= firstline;
state <= WRITING;
end
PRE_READ :
begin
state <= READING;
addr_o <= addr_o + 1;
rd_occ <= 2'b00;
rd_sop <= 1;
rd_eop <= 0;
end
READING :
if(rd_ready_i)
begin
rd_sop <= 0;
addr_o <= addr_o + 1;
if(addr_o == lastline)
begin
rd_eop <= 1;
// FIXME assign occ here
rd_occ <= 0;
end
else
rd_eop <= 0;
if(rd_eop)
state <= DONE;
end
WRITING :
begin
if(wr_ready_i)
begin
addr_o <= addr_o + 1;
if(wr_error)
begin
state <= ERROR;
// Save OCC flags here
end
else if((addr_o == lastline)||wr_eop)
state <= DONE;
end // if (wr_ready_i)
end // case: WRITING
endcase // case(state)
assign dat_to_buf = wr_data_i;
assign rd_data_o = dat_from_buf;
assign rd_flags_o = { rd_occ[1:0], rd_eop, rd_sop };
assign rd_ready_o = (state == READING);
assign wr_sop = wr_flags_i[0];
assign wr_eop = wr_flags_i[1];
assign wr_occ = wr_flags_i[3:2];
assign wr_error = wr_sop & wr_eop;
assign wr_ready_o = (state == WRITING);
assign we_o = (state == WRITING);
//assign we_o = (state == WRITING) && wr_ready_i; // always write to avoid timing issue
assign en_o = ~((state==READING)& ~rd_ready_i); // FIXME potential critical path
assign done = (state == DONE);
assign error = (state == ERROR);
assign idle = (state == IDLE);
endmodule // buffer_int
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