/*
 * This is very similar to design/slave.v, although with 1 important difference
 * - it's meant to be synthesizable (and use iCE40HX8K's embedded RAM).
 */
`default_nettype none

`define ADDR_WIDTH ($clog2(MEMORY_BLOCKS) + 8)

module embedded_bram_slave
  #(
    parameter MEMORY_BLOCKS = 1, /* 1 block stores 256 16-bit words */
    parameter WORDS_TO_INITIALIZE = 0,
    parameter INITIAL_CONTENTS_FILE = "some_file.mem"
    )
   (
    output wire 		   ACK_O,
    input wire 			   CLK_I,
    input wire [`ADDR_WIDTH - 1:0] ADR_I,
    input wire [15:0] 		   DAT_I,
    output wire [15:0] 		   DAT_O,
    input wire 			   RST_I,
    input wire 			   STB_I,
    input wire 			   WE_I,
    output wire 		   STALL_O
    );

   reg [15:0] 			   memory [256 * MEMORY_BLOCKS - 1 : 0];

   generate
      if (WORDS_TO_INITIALIZE) begin
	 initial
	   $readmemb(INITIAL_CONTENTS_FILE, memory, 0, WORDS_TO_INITIALIZE - 1);
      end else begin
	 always @ (posedge CLK_I) begin
	    if (!RST_I && STB_I && WE_I)
	      memory[ADR_I] <= DAT_I;
	 end
      end
   endgenerate

   reg [15:0] output_data;
   reg 	      ack;

   assign DAT_O = output_data;
   assign ACK_O = ack;
   assign STALL_O = 0;

   always @ (posedge CLK_I) begin
      if (RST_I) begin
	 ack <= 0;
      end else begin
	 ack <= STB_I;

	 output_data <= memory[ADR_I];
      end
   end
endmodule // embedded_bram_slave