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//////////////////////////////////////////////////////////////////////////////////
module gpmc
(// GPMC signals
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,
// GPIOs for FIFO signalling
output rx_have_data, output tx_have_space,
// Wishbone signals
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,
// RAM Interface signals
input ram_clk,
input read_en, input [8:0] read_addr, output [31:0] read_data, output read_ready, input read_done,
input write_en, input [8:0] write_addr, input [31:0] write_data, output write_ready, input write_done
);
wire EM_output_enable = (~EM_NOE & (~EM_NCS4 | ~EM_NCS6));
wire [15:0] EM_D_ram;
wire [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
// Writes go into one RAM, reads come from the other
// ////////////////////////////////////////////
// Write path
wire read_sel_in, write_sel_in, clear_in;
wire write_done_in = ~EM_NCS4 & ~EM_NWE & (EM_A == 10'h3FF);
ram_2port_mixed_width buffer_in
(.clk16(wb_clk), .en16(~EM_NCS4), .we16(~EM_NWE), .addr16({write_sel_in,EM_A}), .di16(EM_D), .do16(),
.clk32(ram_clk), .en32(read_en), .we32(0), .addr32({read_sel_in,read_addr}), .di32(0), .do32(read_data));
dbsm dbsm_in(.clk(wb_clk), .reset(wb_rst), .clear(clear_in),
.read_sel(read_sel_in), .read_ready(read_ready), .read_done(read_done),
.write_sel(write_sel_in), .write_ready(tx_have_space), .write_done(write_done_in));
// ////////////////////////////////////////////
// Read path
wire read_sel_out, write_sel_out, clear_out;
wire read_done_out = ~EM_NCS4 & ~EM_NOE & (EM_A == 10'h3FF);
ram_2port_mixed_width buffer_out
(.clk16(wb_clk), .en16(~EM_NCS4), .we16(0), .addr16({read_sel_out,EM_A}), .di16(0), .do16(EM_D_ram),
.clk32(ram_clk), .en32(write_en), .we32(write_en), .addr32({write_sel_out,write_addr}), .di32(write_data), .do32());
dbsm dbsm_out(.clk(wb_clk), .reset(wb_rst), .clear(clear_out),
.read_sel(read_sel_out), .read_ready(rx_have_data), .read_done(read_done_out),
.write_sel(write_sel_out), .write_ready(write_ready), .write_done(write_done));
// 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
reg [15:0] EM_D_wb_reg;
always @(posedge wb_clk)
if(wb_ack_i)
EM_D_wb_reg <= wb_dat_miso;
assign EM_D_wb = wb_ack_i ? wb_dat_miso : EM_D_wb_reg;
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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