Table of Contents

Memory tutorial for USB-FPGA-Modules 2.12, 2.13, 2.14 and 2.18

This tutorial explains the generation of the memory controller IP Core for for the memfifo Example USB-FPGA-Modules 2.12, USB-FPGA-Modules 2.13, USB-FPGA-Modules 2.14 and USB-FPGA-Modules 2.18.

Creating the IP Core

This section describes how the IP Core is created using MIG version 2.1 (Viavado Version 14.2). The settings for other versions should be very similar.

  1. In the Project Manager: click on Memories & Storage Elements → Memory Interface Generators → MIG
  2. Verify the Settings in the first dialog box (FPGA type, speed grade, …)
  3. On the next screen “Create Design” has to be selected and a component name can be entered.
    MIG Screen 2
  4. Here you can chose to create constraints for pin-compatible parts. If you change the part you must replace the constraint file which are a little bit hidden. The constraint for the base part is located in <project name>.srcs/sources_1/ip/<component name>/<component name>/user_design/constraints/<component name>.xdc. This one needs to be replaced by another one from the directory <project name>.srcs/sources_1/ip/<component name>/<component name>/user_design/constraints/compatible_ucf.
    MIG Screen 3
  5. DDR3 memory has to be selected.
    MIG Screen 4
  6. The correct clock period (2500ps) and memory type (MT41J128M16XX-125) have to be entered and “Data mask” should bee enabled.
    MIG screen 5
  7. Chip select must be disabled, on-die termination must be set to RZQ/6 and output impedance control can be set either to RZQ/7 or RZQ/6 (This are the termination settings of the memory component).
    MIG screen 6
  8. System and reference clock buffers must be set to “No buffer” and “Internal Vref” should be disabled.
    MIG screen 7
  9. Input termination must be set to “60 Ohm”. (This is the on-die termination of the FPGA. Due to the output termination of the driver this is not the actual transmission line impedance).
    MIG Screen 8
  10. Fixed pin out has be selected on the next screen.
    MIG Screen 9
  11. In the next dialog box, first click “Read XDC/UCF” and load the file constraints/usb-fga-2.1[3|4]-mem.xdc from SDK package. Then click “validate” and “next”.
    MIG screen 10
  12. The status signals on the next screen are not used.
    MIG screen 11
  13. The last dialog box shows a summary. Click “next” in order to create the core:
    MIG screen 12

Instantiation of the core

Templates with description for instantiation can be found in the file <project name>.srcs/sources_1/ip/<component name>/<component name>.v[o|h]e of the Vivado project.

In the memfifo example this looks like 

    mig_7series_0   mem0 (
// Memory interface ports
	.ddr3_dq(ddr3_dq),
        .ddr3_dqs_n(ddr3_dqs_n),
        .ddr3_dqs_p(ddr3_dqs_p),
        .ddr3_addr(ddr3_addr),
        .ddr3_ba(ddr3_ba),
        .ddr3_ras_n(ddr3_ras_n),
        .ddr3_cas_n(ddr3_cas_n),
        .ddr3_we_n(ddr3_we_n),
        .ddr3_reset_n(ddr3_reset_n),
        .ddr3_ck_p(ddr3_ck_p[0]),
        .ddr3_ck_n(ddr3_ck_n[0]),
        .ddr3_cke(ddr3_cke[0]),
	.ddr3_dm(ddr3_dm),
        .ddr3_odt(ddr3_odt[0]),
// Application interface ports
        .app_addr( {1'b0, app_addr, 3'b000} ),	
        .app_cmd(app_cmd),
        .app_en(app_en),
        .app_rdy(app_rdy),
        .app_wdf_rdy(app_wdf_rdy), 
        .app_wdf_data(app_wdf_data),
        .app_wdf_mask({ APP_MASK_WIDTH {1'b0} }),
        .app_wdf_end(app_wdf_wren), // always the last word in 4:1 mode 
        .app_wdf_wren(app_wdf_wren),
        .app_rd_data(app_rd_data),
        .app_rd_data_end(app_rd_data_end),
        .app_rd_data_valid(app_rd_data_valid),
        .app_sr_req(1'b0), 
        .app_sr_active(),
        .app_ref_req(1'b0),
        .app_ref_ack(),
        .app_zq_req(1'b0),
        .app_zq_ack(),
        .ui_clk(uiclk),
        .ui_clk_sync_rst(ui_clk_sync_rst),
        .init_calib_complete(init_calib_complete),
        .sys_rst(!reset),
// clocks inputs
        .sys_clk_i(clk400),
        .clk_ref_i(clk200)
    );

Clocks on USB-FPGA Modules 2.13

On USB-FPGA Modules 2.13 the clock are generated on-chip from the 48 MHz output clock of the EZ-USB. A PLLE2 is recommended for this purpose as used in the memfifo example: 

    wire pll_fb, clk200, clk400, uiclk, fxclk;
 
    BUFG fxclk_buf (
	.I(fxclk_in),
 	.O(fxclk) 
    );
 
    PLLE2_BASE #(
    	.BANDWIDTH("LOW"),
      	.CLKFBOUT_MULT(25),       		// f_VCO = 1200 MHz (valid: 800 .. 1600 MHz)
      	.CLKFBOUT_PHASE(0.0),
      	.CLKIN1_PERIOD(0.0),
      	.CLKOUT0_DIVIDE(3),			// 400 MHz, memory clock
       	.CLKOUT1_DIVIDE(6),			// 200 MHz, reference clock
      	.CLKOUT2_DIVIDE(CLKOUT2_DIVIDE), 	// unused
      	.CLKOUT3_DIVIDE(CLKOUT3_DIVIDE), 	// unused
       	.CLKOUT4_DIVIDE(CLKOUT4_DIVIDE), 	// unused
      	.CLKOUT5_DIVIDE(CLKOUT5_DIVIDE), 	// unused
      	.CLKOUT0_DUTY_CYCLE(0.5),
      	.CLKOUT1_DUTY_CYCLE(0.5),
      	.CLKOUT2_DUTY_CYCLE(0.5),
      	.CLKOUT3_DUTY_CYCLE(0.5),
       	.CLKOUT4_DUTY_CYCLE(0.5),
      	.CLKOUT5_DUTY_CYCLE(0.5),
      	.CLKOUT0_PHASE(0.0),
      	.CLKOUT1_PHASE(0.0),
      	.CLKOUT2_PHASE(CLKOUT2_PHASE),
      	.CLKOUT3_PHASE(CLKOUT3_PHASE),
       	.CLKOUT4_PHASE(CLKOUT4_PHASE),
      	.CLKOUT5_PHASE(CLKOUT5_PHASE),
       	.DIVCLK_DIVIDE(1),
      	.REF_JITTER1(0.0),
      	.STARTUP_WAIT("FALSE")
    )
    dram_fifo_pll_inst (
      	.CLKIN1(fxclk),		// 48 MHz input clock
      	.CLKOUT0(clk400),	// 400 MHz memory clock
      	.CLKOUT1(clk200),       // 200 MHz reference clock
      	.CLKOUT2(),   
      	.CLKOUT3(),   
      	.CLKOUT4(),   
      	.CLKOUT5(),   
      	.CLKFBOUT(pll_fb),
      	.CLKFBIN(pll_fb),
      	.PWRDWN(1'b0),
      	.RST(1'b0)
    );

Clocks on USB-FPGA Modules 2.14 and 2.18

On USB-FPGA Modules 2.14 and 2.18 the clock are generated on-chip from the 26 MHz on-bord oscilator. A PLLE2 is recommended for this purpose as used in the memfifo example: 

    wire pll_fb, clk200, clk400, uiclk, fxclk;
    wire pll_fb, clk200_in, clk400_in, clk200, clk400, uiclk, fxclk;
 
    BUFG fxclk_buf (
	.I(fxclk_in),
	.O(fxclk) 
    );
 
    BUFG clk200_buf (  		// sometimes it is generated automatically, sometimes not ...
	.I(clk200_in),
	.O(clk200) 
    );
 
    BUFG clk400_buf (
	.I(clk400_in),
	.O(clk400) 
    );
 
    PLLE2_BASE #(
    	.BANDWIDTH("LOW"),
      	.CLKFBOUT_MULT(31),     // f_VCO = 806 MHz (valid: 800 .. 1600 MHz)
      	.CLKFBOUT_PHASE(0.0),
      	.CLKIN1_PERIOD(0.0),
      	.CLKOUT0_DIVIDE(2),	// 403 Mz
      	.CLKOUT1_DIVIDE(4),	// 201.5 MHz
      	.CLKOUT2_DIVIDE(CLKOUT2_DIVIDE),
      	.CLKOUT3_DIVIDE(CLKOUT3_DIVIDE),
      	.CLKOUT4_DIVIDE(CLKOUT4_DIVIDE),
      	.CLKOUT5_DIVIDE(CLKOUT5_DIVIDE),
      	.CLKOUT0_DUTY_CYCLE(0.5),
      	.CLKOUT1_DUTY_CYCLE(0.5),
      	.CLKOUT2_DUTY_CYCLE(0.5),
      	.CLKOUT3_DUTY_CYCLE(0.5),
      	.CLKOUT4_DUTY_CYCLE(0.5),
      	.CLKOUT5_DUTY_CYCLE(0.5),
      	.CLKOUT0_PHASE(0.0),
      	.CLKOUT1_PHASE(0.0),
      	.CLKOUT2_PHASE(CLKOUT2_PHASE),
      	.CLKOUT3_PHASE(CLKOUT3_PHASE),
      	.CLKOUT4_PHASE(CLKOUT4_PHASE),
      	.CLKOUT5_PHASE(CLKOUT5_PHASE),
      	.DIVCLK_DIVIDE(1),
      	.REF_JITTER1(0.0),
      	.STARTUP_WAIT("FALSE")
    )
    dram_fifo_pll_inst (
      	.CLKIN1(fxclk),
      	.CLKOUT0(clk400_in),
      	.CLKOUT1(clk200_in),   
      	.CLKOUT2(clkout2),   
      	.CLKOUT3(clkout3),   
      	.CLKOUT4(clkout4),   
      	.CLKOUT5(clkout5),   
      	.CLKFBOUT(pll_fb),
      	.CLKFBIN(pll_fb),
      	.PWRDWN(1'b0),
      	.RST(1'b0)
    );