module gpmc_to_fifo_async (input [15:0] EM_D, input [1:0] EM_NBE, input EM_NCS, input EM_NWE, input fifo_clk, input fifo_rst, output reg [17:0] data_o, output reg src_rdy_o, input dst_rdy_i, input [15:0] frame_len, input [15:0] fifo_space, output fifo_ready, output reg bus_error ); reg [10:0] counter; // Synchronize the async control signals reg [1:0] cs_del, we_del; always @(posedge fifo_clk) if(fifo_rst) begin cs_del <= 2'b11; we_del <= 2'b11; end else begin cs_del <= { cs_del[0], EM_NCS }; we_del <= { we_del[0], EM_NWE }; end wire do_write = (~cs_del[0] & (we_del == 2'b10)); wire first_write = (counter == 0); wire last_write = ((counter+1) == frame_len); always @(posedge fifo_clk) if(do_write) begin data_o[15:0] <= EM_D; data_o[16] <= first_write; data_o[17] <= last_write; // no byte writes data_o[18] <= |EM_NBE; // mark half full if either is not enabled FIXME end always @(posedge fifo_clk) if(fifo_rst) src_rdy_o <= 0; else if(do_write) src_rdy_o <= 1; else src_rdy_o <= 0; // Assume it was taken always @(posedge fifo_clk) if(fifo_rst) counter <= 0; else if(do_write) if(last_write) counter <= 0; else counter <= counter + 1; assign fifo_ready = first_write & (fifo_space > frame_len); always @(posedge fifo_clk) if(fifo_rst) bus_error <= 0; else if(src_rdy_o & ~dst_rdy_i) bus_error <= 1; endmodule // gpmc_to_fifo_async