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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 BUFF_NUM = 0)
(// 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 [8:0] addr_o,
output [31:0] dat_to_buf,
input [31:0] dat_from_buf,
// Write FIFO Interface
input [31:0] wr_dat_i,
input wr_write_i,
input wr_done_i,
input wr_error_i,
output reg wr_ready_o,
output reg wr_full_o,
// Read FIFO Interface
output [31:0] rd_dat_o,
input rd_read_i,
input rd_done_i,
input rd_error_i,
output reg rd_sop_o,
output reg rd_eop_o
);
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] == BUFF_NUM))
ctrl_reg <= ctrl_word;
wire [8:0] firstline = ctrl_reg[8:0];
wire [8:0] lastline = ctrl_reg[17:9];
wire [3:0] step = ctrl_reg[21:18];
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 ?
assign dat_to_buf = wr_dat_i;
assign rd_dat_o = dat_from_buf;
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;
always @(posedge clk)
if(rst)
begin
state <= IDLE;
rd_sop_o <= 0;
rd_eop_o <= 0;
wr_ready_o <= 0;
wr_full_o <= 0;
end
else
if(clear)
begin
state <= IDLE;
rd_sop_o <= 0;
rd_eop_o <= 0;
wr_ready_o <= 0;
wr_full_o <= 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;
wr_ready_o <= 1;
end
PRE_READ :
begin
state <= READING;
addr_o <= addr_o + 1;
rd_sop_o <= 1;
end
READING :
if(rd_error_i)
state <= ERROR;
else if(rd_done_i)
state <= DONE;
else if(rd_read_i)
begin
rd_sop_o <= 0;
addr_o <= addr_o + 1;
if(addr_o == lastline)
rd_eop_o <= 1;
else
rd_eop_o <= 0;
if(rd_eop_o)
state <= DONE;
end
WRITING :
begin
if(wr_write_i)
addr_o <= addr_o + 1; // This was the timing problem, so now it doesn't depend on wr_error_i
if(wr_error_i)
begin
state <= ERROR;
wr_ready_o <= 0;
end
else
begin
if(wr_write_i)
begin
wr_ready_o <= 0;
if(addr_o == (lastline-1))
wr_full_o <= 1;
if(addr_o == lastline)
state <= DONE;
end
if(wr_done_i)
begin
state <= DONE;
wr_ready_o <= 0;
end
end // else: !if(wr_error_i)
end // case: WRITING
DONE :
begin
rd_eop_o <= 0;
rd_sop_o <= 0;
wr_ready_o <= 0;
wr_full_o <= 0;
end
endcase // case(state)
// FIXME ignores step for now
assign we_o = (state == WRITING) && wr_write_i; // FIXME potential critical path
// IF this is a timing problem, we could always write when in this state
assign en_o = ~((state==READING)& ~rd_read_i); // FIXME potential critical path
assign done = (state == DONE);
assign error = (state == ERROR);
assign idle = (state == IDLE);
endmodule // buffer_int
// These are 2 other ways for doing the WRITING state, both work. First one is faster, but confusing
/*
begin
// Gen 4 values -- state, wr_ready_o, addr_o, wr_full_o
if(~wr_error_i & wr_write_i & (addr_o == (lastline-1)))
wr_full_o <= 1;
if(wr_error_i | wr_write_i | wr_done_i)
wr_ready_o <= 0;
if(wr_error_i)
state <= ERROR;
else if(wr_done_i | (wr_write_i & (addr_o == lastline)))
state <= DONE;
// This one was the timing problem... now we increment addr_o even if there is an error
if(wr_write_i)
addr_o <= addr_o + 1;
end // case: WRITING
*/
/* begin
if(wr_error_i)
begin
state <= ERROR;
wr_ready_o <= 0;
end
else
begin
if(wr_write_i)
begin
wr_ready_o <= 0;
addr_o <= addr_o + 1;
if(addr_o == (lastline-1))
wr_full_o <= 1;
if(addr_o == lastline)
state <= DONE;
end
if(wr_done_i)
begin
state <= DONE;
wr_ready_o <= 0;
end
end // else: !if(wr_error_i)
end // case: WRITING
*/
// Unused old code
//assign rd_empty_o = (state != READING); // && (state != PRE_READ);
//assign rd_empty_o = rd_empty_reg; // timing fix?
//assign rd_ready_o = (state == READING);
//assign rd_ready_o = ~rd_empty_reg; // timing fix?
//wire rd_en = (state == PRE_READ) || ((state == READING) && rd_read_i);
//wire wr_en = (state == WRITING) && wr_write_i; // IF this is a timing problem, we could always enable when in this state
//assign en_o = rd_en | wr_en;
// assign wr_full_o = (state != WRITING);
// assign wr_ready_o = (state == WRITING);
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