Use Clocking Wizard v1.4 core's output to update the CLOCK_MODULE to the above mentioned issues. The Clocking Wizard can be found under 'FPGA Features and Design'/'Clocking' taxonomy in the CORE Generator software.
The Aurora 64B66B Core instantiates two MMCM components, one in CLOCK_MODULE and another in GTX_WRAPPER.
- The MMCM inside the CLOCK_MODULE is present inside <generated core component name>\example_design\clock_module.
- The MMCM inside the GTX_WRAPPER is present inside <generated core component name>\example_design\gtx\<generated core component name>_wrapper.
The following table shows the Aurora 64B66B Core's clock_module and gtx_wrapper parameters with respect to MMCM attributes:
Clocking Wizard's MMCM
|
Aurora 64B66B Core's MMCM
|
CLKFBOUT_MULT_F
|
MULT
|
DIVICLK_DIVIDE
|
DIVIDE
|
CLKIN1_PERIOD
|
CLK_PERIOD
|
CLKOUT0_DIVIDE_F
|
OUT0_DIVIDE
|
CLKOUT1_DIVIDE
|
OUT1_DIVIDE
|
CLKOUT2_DIVIDE
|
OUT2_DIVIDE
|
CLKOUT3_DIVIDE
|
OUT3_DIVIDE
|
To generate the MMCM component, the Clocking Wizard requires the input frequency, i.e., CLKIN1_FREQ and the output frequency. Use the next procedure to calculate the required input and output frequency values.
1. Input frequency calculation.
- Input frequency is calculated as (Line rate/16)*1000
- Line Rate is Aurora 64B66B core parameter and refers to c_line_rate parameter in the XCO file.
- Enter this value as the primary input clock frequency in the Clocking Wizard GUI on page 1.
2. Output frequency1 calculation.
- Output frequency1 = ((Line rate/16)*1000) (in MHz)
- Enter this value as CLK_OUT1 in the Clocking Wizard GUI on page 2.
3. Output frequency2 calculation.
- Output frequency2 = ((Line rate/16)*1000)/2 (in MHz)
- Output frequency2 is same as the primary input clock frequency calculated in Step 1.
- Enter this value as CLK_OUT2 in the Clocking Wizard GUI on page 2.
- Make sure to select the CLK_OUT2 checkbox.
4. Output frequency3 calculation.
- Output frequency3 = ((Line rate/16)*1000)/4 (in MHz)
- Output frequency3 is same as Primary input clock frequency calculated in Step 1.
- Enter this value as CLK_OUT3 in the Clocking Wizard GUI on page 2.
- Make sure to select the CLK_OUT3 check box.
The Clocking wizard displays all the MMCM attribute values on page 4 of the GUI after the above mentioned steps are followed.
Use the values displayed on page 4 of the GUI to update the Aurora 64B66B Core's CLOCK_MODULE and GTX_WRAPPER, or use the Clocking Wizard Core generated template values to update CLOCK_MODULE and GTX_WRAPPER.
MMCM uses the following simplified formula to calculate VCO frequency range:
VCO Frequency = (CLKFBOUT_MULT_F/DIVCLK_DIVIDE)*CLKIN1_FREQ
Use the above formula and
Virtex-6 FPGA Clocking Resources User Guide (UG362) as additional references.