Initial commit of OpenSPARC T2 design and verification files.

[OpenSPARC-T2-DV] / verif / env / common / verilog / misc / fifo.v

// ========== Copyright Header Begin ==========================================
// 
// OpenSPARC T2 Processor File: fifo.v
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// ========== Copyright Header End ============================================
module fifo ();

parameter ENTRY_BITS = 5;
parameter DEPTH      = 9;
parameter PTR_BITS   = 4;

reg   [(ENTRY_BITS-1):0] fifo [0:(DEPTH-1)];
reg     [(PTR_BITS-1):0] push_ptr;
reg     [(PTR_BITS-1):0] pop_ptr;

integer                  i;

`ifdef DEBUG_FIFO
 wire [(ENTRY_BITS-1):0] fifo0 = fifo[0];
 wire [(ENTRY_BITS-1):0] fifo1 = fifo[1];
 wire [(ENTRY_BITS-1):0] fifo2 = fifo[2];
 wire [(ENTRY_BITS-1):0] fifo3 = fifo[3];
 wire [(ENTRY_BITS-1):0] fifo4 = fifo[4];
 wire [(ENTRY_BITS-1):0] fifo5 = fifo[5];
 wire [(ENTRY_BITS-1):0] fifo6 = fifo[6];
 wire [(ENTRY_BITS-1):0] fifo7 = fifo[7];
`endif

//----------------------------------------------------------
initial  begin // {
`ifdef PALLADIUM
`else
 #1;
`endif
 push_ptr = 3'b0;
 pop_ptr = 3'b0;
 for (i=0; i<=(DEPTH-1); i=i+1) begin
   fifo[i] = 0;
 end  
end // }

//----------------------------------------------------------
task push_fifo;
input [(ENTRY_BITS-1):0] entry;

 begin
    fifo[push_ptr] <= entry;
    if (push_ptr == (DEPTH-1)) begin // {
       push_ptr <= 3'b0;
       // Check for Overflow
       if (pop_ptr == 3'b0)  begin // {
         `PR_ERROR ("fifo", `ERROR, "FIFO Overflow.");
       end // }
    end // }
    else begin // {
       push_ptr <= push_ptr + 1;
       // Check for Overflow
       if (pop_ptr == push_ptr+1)  begin // {
         `PR_ERROR ("fifo", `ERROR, "FIFO Overflow.");
       end // }
    end // }

 end
endtask

//----------------------------------------------------------
task pop_fifo;
output [(ENTRY_BITS-1):0] entry;

 begin
    // Check for Underflow
    if (pop_ptr == push_ptr) begin
     `PR_ERROR ("fifo", `ERROR, "FIFO Underflow.");
    end

    entry = fifo[pop_ptr];
    fifo[pop_ptr] <= 0;  // clear entry that was popped
    if (pop_ptr == (DEPTH-1)) begin // {
       pop_ptr <= 3'b0;
    end // }
    else begin // {
       pop_ptr <= pop_ptr + 1;
    end // }
 end
endtask

endmodule

//----------------------------------------------------------
//----------------------------------------------------------