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module fifo #(
parameter DATA_WIDTH = 8,
parameter DATA_DEPTH = 1024
) (
input rst_i,
input clk_i,
input write_i,
input read_i,
output empty_o,
output full_o,
//output data_valid_o,
input [(DATA_WIDTH-1) : 0] data_i,
output reg [(DATA_WIDTH-1) : 0] data_o
);
// need to "count" to number *including* depth
reg [$clog2(DATA_DEPTH + 1)-1:0] r_count;
reg [(DATA_WIDTH-1) : 0] r_datastore [(DATA_DEPTH-1) : 0];
reg [$clog2(DATA_DEPTH)-1:0] r_read_addr;
reg [$clog2(DATA_DEPTH)-1:0] r_write_addr;
initial begin
r_count = 0;
r_read_addr = 0;
r_write_addr = 0;
end
always @(posedge clk_i or negedge rst_i) begin
if (!rst_i) begin
r_count <= 0;
r_read_addr <= 0;
r_write_addr <= 0;
end else if (write_i && read_i) begin
// nothing to do
end else if (write_i && !full_o) begin
r_count <= r_count + 1;
r_datastore[r_write_addr] <= data_i;
// the_verilator wrongly (???) assumes DATA_DEPTH-1 requires 1 more bit than it does?
if ({1'b0, r_write_addr} < (DATA_DEPTH - 1))
r_write_addr <= r_write_addr + 1;
else
r_write_addr <= 0;
end else if (read_i && !empty_o) begin
r_count <= r_count - 1;
data_o <= r_datastore[r_read_addr];
// the_verilator wrongly (???) assumes DATA_DEPTH-1 requires 1 more bit than it does?
if ({1'b0, r_read_addr} < (DATA_DEPTH - 1))
r_read_addr <= r_read_addr + 1;
else
r_read_addr <= 0;
end
end
assign empty_o = r_count == 0;
assign full_o = r_count == DATA_DEPTH;
endmodule
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