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`timescale 1ns / 1ps
//////////////////////////////////////////////////////////////////////////////////
module gpmc
(input EM_CLK, inout [15:0] EM_D, input [10:1] EM_A, input [1:0] EM_NBE,
input EM_WAIT0, input EM_NCS4, input EM_NCS6, input EM_NWE, input EM_NOE,
input wb_clk, input wb_rst,
output reg [10:0] wb_adr_o, output reg [15:0] wb_dat_mosi, input [15:0] wb_dat_miso,
output reg [1:0] wb_sel_o, output wb_cyc_o, output reg wb_stb_o, output reg wb_we_o, input wb_ack_i
);
wire EM_output_enable = (~EM_NOE & (~EM_NCS4 | ~EM_NCS6));
wire [15:0] EM_D_ram;
reg [15:0] EM_D_wb;
assign EM_D = ~EM_output_enable ? 16'bz : ~EM_NCS4 ? EM_D_ram : EM_D_wb;
// CS4 is RAM_2PORT for high-speed data
ram_2port #(.DWIDTH(16), .AWIDTH(10)) ram_2port
(.clka(clk_fpga), .ena(~EM_NCS4), .wea(~EM_NWE), .addra(EM_A), .dia(EM_D), .doa(EM_D_ram),
.clkb(clk_fpga), .enb(0), .web(0), .addrb(0), .dib(0), .dob());
// CS6 is Control, Wishbone bus bridge (wb master)
// Sync version
reg [1:0] cs_del, we_del, oe_del;
// Synchronize the async control signals
always @(posedge wb_clk)
begin
cs_del <= { cs_del[0], EM_NCS6 };
we_del <= { we_del[0], EM_NWE };
oe_del <= { oe_del[0], EM_NOE };
end
always @(posedge wb_clk)
if(cs_del == 2'b10) // Falling Edge
wb_adr_o <= { EM_A, 1'b0 };
always @(posedge wb_clk)
if(we_del == 2'b10) // Falling Edge
begin
wb_dat_mosi <= EM_D;
wb_sel_o <= ~EM_NBE;
end
always @(posedge wb_clk)
if(wb_ack_i)
EM_D_wb <= wb_dat_miso;
// stb, oe_del, we_del
assign wb_cyc_o = wb_stb_o;
always @(posedge wb_clk)
if( ~cs_del[0] & (we_del == 2'b10) )
wb_we_o <= 1;
else if(wb_ack_i) // Turn off we when done. Could also use we_del[0], others...
wb_we_o <= 0;
always @(posedge wb_clk)
if( ~cs_del[0] & ((we_del == 2'b10) | (oe_del == 2'b10)))
wb_stb_o <= 1;
else if(wb_ack_i)
wb_stb_o <= 0;
endmodule // gpmc
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