FPGA Clock/Trigger generator

• DLL1: CLKIN=32MHz -> *25, /8 -> 100MHz
• DLL2: CLKIN=100Mhz -> *5, /7 -> 71.428MHz
• DLL3: CLKIN=71.428MHz/2
• DLL4: CLKIN=142.86MHz

converting frequencies using DCM module VHDL code

MR <=MR1 xor MR2
MR1<=CLKIN3
MR2<=CLKIN3, variable phase delayed

CCR <= 
  if rising_edge(CLKIN4) then
    CCR<=trigger xor CCRCLK;
    CCRCLK<=not CCRCLK;
  fi

differential signals

Measurements

When defining an output as LVDS_25 (VCCO jumper to 3.3V):

• Voltage over + and - pair: 0.559 / -0.558 V
• Current (when shorted): 10.69/-10.62 mA
• Voltage over GND and + (or -): 1.53 / 0.97V

VCCO Jumper to 2.5V:

• Voltage over + and - pair: 0.567 / -0.565 V
• Current (when shorted): 10.71 / -10.64 mA
• Voltage over GND and + (or -): 1.53 / 0.97V

VCCO Jumper to 1.2V:

• Voltage over + and - pair: ? / -0.5228 V
• Current (when shorted): ? / 4.59 mA
• Voltage over GND and + / - : 0.27 / 0.79 V

Available Lines

As I'm using (4 pins on) the right-side for the DX Display TM1638 connection, I try to only use the left side; some of the available differential pins are:

• C2/C3 = P94/P95 = IO_L06 (P94 connected to single-signal)
• C5/C6 = P2/P3 = IO_L01
• C7/C8 = P4/P5 = IO_L02
• C9/C10 = P9/P10 = IO_L03 (P9/P10 connected to differential)

Xilinx code to drive Differential signals

information copied from Hamster Code

NET test_sig_out_n LOC = "P12"; # C12
NET test_sig_out_p LOC = "P11"; # C11

NET test_sig_in_p LOC = "P15"; # C13
NET test_sig_in_n LOC = "P16"; # C14

Then, to drive/read the differential signals, use in VHDL:

library UNISIM;
use UNISIM.VComponents.all;
--
--
output_buffer: OBUFDS 
   generic map ( IOSTANDARD => "LVDS_25") 
   port map (
      O => test_sig_out_p, 
      OB => test_sig_out_n,
      I => test_sig_out    
   );
input_buffer : IBUFDS 
   generic map (
      DIFF_TERM => TRUE,
      IBUF_DELAY_VALUE => "0", 
      IFD_DELAY_VALUE => "AUTO",
      IOSTANDARD => "LVDS_25")
   port map (
      O  => test_sig_in,   -- Buffer output
      I  => test_sig_in_p, -- Diff_p buffer input (connect directly to top-level port)
      IB => test_sig_in_n  -- Diff_n buffer input (connect directly to top-level port)
   );