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Diffstat (limited to 'fpga/usrp2/extramfifo/ext_fifo.v')
| -rw-r--r-- | fpga/usrp2/extramfifo/ext_fifo.v | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/fpga/usrp2/extramfifo/ext_fifo.v b/fpga/usrp2/extramfifo/ext_fifo.v new file mode 100644 index 000000000..2af59a75d --- /dev/null +++ b/fpga/usrp2/extramfifo/ext_fifo.v @@ -0,0 +1,123 @@ +// +// FIFO backed by an off chip ZBT/NoBL SRAM. +// +// This module and its sub-hierarchy implment a FIFO capable of sustaining +// a data throughput rate of at least int_clk/2 * 36bits and bursts of int_clk * 36bits. +// +// This has been designed and tested for an int_clk of 100MHz and an ext_clk of 125MHz, +// your milage may vary with other clock ratio's especially those where int_clk < ext_clk. +// Testing has also exclusively used a rst signal synchronized to int_clk. +// +// Interface operation mimics a Xilinx FIFO configured as "First Word Fall Through", +// though signal naming differs. +// +// For FPGA use registers interfacing directly with signals prefixed "RAM_*" should be +// packed into the IO ring. +// + + //`define NO_EXT_FIFO + +module ext_fifo + #(parameter INT_WIDTH=36,EXT_WIDTH=18,RAM_DEPTH=19,FIFO_DEPTH=19) + ( + input int_clk, + input ext_clk, + input rst, + input [EXT_WIDTH-1:0] RAM_D_pi, + output [EXT_WIDTH-1:0] RAM_D_po, + output RAM_D_poe, + output [RAM_DEPTH-1:0] RAM_A, + output RAM_WEn, + output RAM_CENn, + output RAM_LDn, + output RAM_OEn, + output RAM_CE1n, + input [INT_WIDTH-1:0] datain, + input src_rdy_i, // WRITE + output dst_rdy_o, // not FULL + output [INT_WIDTH-1:0] dataout, + output src_rdy_o, // not EMPTY + input dst_rdy_i, // READ + output reg [31:0] debug, + output reg [31:0] debug2 + ); + + wire [EXT_WIDTH-1:0] write_data; + wire [EXT_WIDTH-1:0] read_data; + wire full1, empty1; + wire almost_full2, full2, empty2; + wire [INT_WIDTH-1:0] data_to_fifo; + wire [INT_WIDTH-1:0] data_from_fifo; + wire [FIFO_DEPTH-1:0] capacity; + + + // FIFO buffers data from UDP engine into external FIFO clock domain. + fifo_xlnx_512x36_2clk_36to18 fifo_xlnx_512x36_2clk_36to18_i1 ( + .rst(rst), + .wr_clk(int_clk), + .rd_clk(ext_clk), + .din(datain), // Bus [35 : 0] + .wr_en(src_rdy_i), + .rd_en(space_avail&~empty1), + .dout(write_data), // Bus [17 : 0] + .full(full1), + .empty(empty1)); + + assign dst_rdy_o = ~full1; + +`ifdef NO_EXT_FIFO + assign space_avail = ~full2; + assign data_avail = ~empty1; + assign read_data = write_data; +`else + + // External FIFO running at ext clock rate and 18 bit width. + nobl_fifo #(.WIDTH(EXT_WIDTH),.RAM_DEPTH(RAM_DEPTH),.FIFO_DEPTH(FIFO_DEPTH)) + nobl_fifo_i1 + ( + .clk(ext_clk), + .rst(rst), + .RAM_D_pi(RAM_D_pi), + .RAM_D_po(RAM_D_po), + .RAM_D_poe(RAM_D_poe), + .RAM_A(RAM_A), + .RAM_WEn(RAM_WEn), + .RAM_CENn(RAM_CENn), + .RAM_LDn(RAM_LDn), + .RAM_OEn(RAM_OEn), + .RAM_CE1n(RAM_CE1n), + .write_data(write_data), + .write_strobe(~empty1 ), + .space_avail(space_avail), + .read_data(read_data), + .read_strobe(~almost_full2), + .data_avail(data_avail), + .capacity(capacity) + ); +`endif // !`ifdef NO_EXT_FIFO + + + // FIFO buffers data read from external FIFO into DSP clk domain and to TX DSP. + fifo_xlnx_512x36_2clk_18to36 fifo_xlnx_512x36_2clk_18to36_i1 ( + .rst(rst), + .wr_clk(ext_clk), + .rd_clk(int_clk), + .din(read_data), // Bus [17 : 0] + .wr_en(data_avail), + .rd_en(dst_rdy_i), + .dout(dataout), // Bus [35 : 0] + .full(full2), + .prog_full(almost_full2), + .empty(empty2)); + assign src_rdy_o = ~empty2; + + always @ (posedge int_clk) + debug[31:28] <= {empty2,full1,dst_rdy_i,src_rdy_i }; + + always @ (posedge ext_clk) + debug[27:0] <= {RAM_WEn,RAM_CE1n,RAM_A[3:0],read_data[17:0],empty1,space_avail,data_avail,almost_full2 }; + + always@ (posedge ext_clk) +// debug2[31:0] <= {write_data[15:0],read_data[15:0]}; + debug2[31:0] <= 0; +endmodule // ext_fifo |