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  3. AR# 34190: Virtex-6 GTX Aurora 64b/66b - MAP errors out due to incorrect MMCM attributes

AR# 34190

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Virtex-6 GTX Aurora 64b/66b - MAP errors out due to incorrect MMCM attributes

描述

The Aurora 64B66B Core uses 400 MHz as the lowest frequency limit for the MMCM's VCO.

This limit is increased to 600 MHz based on characterization data for all Virtex-6 and Virtex-6 -1L devices.

MAP errors out for cores that do not meet the VCO frequency range.

Apart from this issue, MAP generates an error when using the values 1, 2, 3, or 4 or fractional values for CLKFBOUT_MULT_F in MMCM_ADV.

解决方案

Use the Clocking Wizard v1.4 core's output to update the CLOCK_MODULE for 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, (iCLKIN1_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 an Aurora 64B66B core parameter and refers to the 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 the 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 the same as the 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 of 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.

http://www.xilinx.com/support/documentation/user_guides/ug362.pdf

AR# 34190
日期 03/10/2015
状态 Active
Type 综合文章
器件
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