Subversion Repositories openrisc_me

module ram_wb ( dat_i, dat_o, adr_i, we_i, sel_i, cyc_i, stb_i, ack_o, cti_i, clk_i, rst_i);
 
   parameter dat_width = 32;
   parameter adr_width = 12;
   parameter mem_size  = 262144; // Default is 1MB (262144 32-bit words)
 
   // wishbone signals
   input [31:0]          dat_i;   
   output [31:0]         dat_o;
   input [adr_width-1:2] adr_i;
   input 		 we_i;
   input [3:0] 		 sel_i;
   input 		 cyc_i;
   input 		 stb_i;
   output reg 		 ack_o;
   input [2:0] 		 cti_i;
 
   // clock
   input 		 clk_i;
   // async reset
   input 		 rst_i;
 
   wire [31:0] 		 wr_data;
 
   // mux for data to ram
   assign wr_data[31:24] = sel_i[3] ? dat_i[31:24] : dat_o[31:24];
   assign wr_data[23:16] = sel_i[2] ? dat_i[23:16] : dat_o[23:16];
   assign wr_data[15: 8] = sel_i[1] ? dat_i[15: 8] : dat_o[15: 8];
   assign wr_data[ 7: 0] = sel_i[0] ? dat_i[ 7: 0] : dat_o[ 7: 0];
 
   ram_wb_sc_sw
     #
     (
      .dat_width(dat_width),
      .adr_width(adr_width),
      .mem_size(mem_size)
      )
     ram0
     (
      .dat_i(wr_data),
      .dat_o(dat_o),
      .adr_i({2'b00, adr_i}), 
      .we_i(we_i & ack_o),
      .clk(clk_i)
      );
 
   // ack_o
   always @ (posedge clk_i or posedge rst_i)
     if (rst_i)
       ack_o <= 1'b0;
     else
       if (!ack_o) 
	 begin
	    if (cyc_i & stb_i)
	      ack_o <= 1'b1; 
	 end
       else
	 ack_o <= 1'b0;
 
   // We did have acking logic which was sensitive to the
   // burst signals, cti_i, but this proved to cause problems
   // and we were never receiving back-to-back reads or writes
   // anyway. This logic which only acks one transaction at a
   // time appears to work well, despite not supporting burst
   // transactions.
 
endmodule