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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_int2
#(parameter BASE = 0,
parameter BUF_SIZE = 9)
(input clk, input rst,
input set_stb, input [7:0] set_addr, input [31:0] set_data,
output [31:0] status,
// Wishbone interface to RAM
input wb_clk_i,
input wb_rst_i,
input wb_we_i,
input wb_stb_i,
input [15:0] wb_adr_i,
input [31:0] wb_dat_i,
output [31:0] wb_dat_o,
output reg wb_ack_o,
// Write FIFO Interface
input [35:0] wr_data_i,
input wr_ready_i,
output wr_ready_o,
// Read FIFO Interface
output [35:0] rd_data_o,
output rd_ready_o,
input rd_ready_i
);
reg [15:0] rd_addr, wr_addr; // Handle pkt bigger than buffer
wire [15:0] rd_addr_next = rd_addr + 1;
reg [15:0] rd_length;
wire [31:0] ctrl;
wire wr_done, wr_error, wr_idle;
wire rd_done, rd_error, rd_idle;
wire we, en, go;
wire read = ctrl[3];
wire rd_clear = ctrl[2];
wire write = ctrl[1];
wire wr_clear = ctrl[0];
reg [2:0] rd_state, wr_state;
reg rd_sop, rd_eop;
wire wr_sop, wr_eop;
reg [1:0] rd_occ;
wire [1:0] wr_occ;
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;
// read state machine
always @(posedge clk)
if(rst | (rd_clear & go))
begin
rd_state <= IDLE;
rd_sop <= 0;
rd_eop <= 0;
rd_occ <= 0;
end
else
case(rd_state)
IDLE :
if(go & read)
begin
rd_addr <= 0;
rd_state <= PRE_READ;
rd_length <= ctrl[31:16];
end
PRE_READ :
begin
rd_state <= READING;
rd_addr <= rd_addr_next;
rd_occ <= 2'b00;
rd_sop <= 1;
rd_eop <= 0;
end
READING :
if(rd_ready_i)
begin
rd_sop <= 0;
rd_addr <= rd_addr_next;
if(rd_addr_next == rd_length)
begin
rd_eop <= 1;
// FIXME assign occ here
rd_occ <= 0;
end
else
rd_eop <= 0;
if(rd_eop)
rd_state <= DONE;
end
endcase // case(rd_state)
// write state machine
always @(posedge clk)
if(rst | (wr_clear & go))
wr_state <= IDLE;
else
case(wr_state)
IDLE :
if(go & write)
begin
wr_addr <= 0;
wr_state <= WRITING;
end
WRITING :
if(wr_ready_i)
begin
wr_addr <= wr_addr + 1;
if(wr_sop & wr_eop)
wr_state <= ERROR; // Should save OCC flags here
else if(wr_eop)
wr_state <= DONE;
end // if (wr_ready_i)
endcase // case(wr_state)
assign rd_data_o[35:32] = { rd_occ[1:0], rd_eop, rd_sop };
assign rd_ready_o = (rd_state == READING);
assign wr_sop = wr_data_i[32];
assign wr_eop = wr_data_i[33];
assign wr_occ = wr_data_i[35:34];
assign wr_ready_o = (wr_state == WRITING);
assign we = (wr_state == WRITING); // always write to avoid timing issue
assign en = ~((rd_state==READING)& ~rd_ready_i); // FIXME potential critical path
assign rd_done = (rd_state == DONE);
assign wr_done = (wr_state == DONE);
assign rd_error = (rd_state == ERROR);
assign wr_error = (wr_state == ERROR);
assign rd_idle = (rd_state == IDLE);
assign wr_idle = (wr_state == IDLE);
wire [BUF_SIZE-1:0] wr_addr_clip = (|wr_addr[15:BUF_SIZE]) ? {BUF_SIZE{1'b1}} : wr_addr[BUF_SIZE-1:0];
ram_2port #(.DWIDTH(32),.AWIDTH(BUF_SIZE)) buffer_in // CPU reads here
(.clka(wb_clk_i),.ena(wb_stb_i),.wea(1'b0),
.addra(wb_adr_i[BUF_SIZE+1:2]),.dia(0),.doa(wb_dat_o),
.clkb(clk),.enb(1'b1),.web(we),
.addrb(wr_addr_clip),.dib(wr_data_i[31:0]),.dob());
ram_2port #(.DWIDTH(32),.AWIDTH(BUF_SIZE)) buffer_out // CPU writes here
(.clka(wb_clk_i),.ena(wb_stb_i),.wea(wb_we_i),
.addra(wb_adr_i[BUF_SIZE+1:2]),.dia(wb_dat_i),.doa(),
.clkb(clk),.enb(en),.web(1'b0),
.addrb(rd_addr[BUF_SIZE-1:0]),.dib(0),.dob(rd_data_o[31:0]));
always @(posedge wb_clk_i)
if(wb_rst_i)
wb_ack_o <= 0;
else
wb_ack_o <= wb_stb_i & ~wb_ack_o;
setting_reg #(.my_addr(BASE))
sreg(.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),.in(set_data),
.out(ctrl),.changed(go));
assign status = { wr_addr,
8'b0,1'b0,rd_idle,rd_error,rd_done, 1'b0,wr_idle,wr_error,wr_done};
endmodule // buffer_int2
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