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8,565 Views
Registered: ‎03-02-2015

## Output clock frequency in clocking Wizard,Virtex 7

Hi,

I have a clock with frequency 337.5 MHz.I want to create some output clocks based on my input clock using Clocking Wizard in Vivado 2014.4

In clocking wizard,do we have a limitation on the value of o/p clock frequency dependent on i/p clock ?

For example:- I have a input clock of x MHz,am i restricted to having o/p clocks of either x,2*x,4*x,.......,x/2,x/4.......etc.. ?

From 337.5 MHz, i want a clock of 156.25 MHz,it is not generating it ?It either does 149.xx or 168.75.no value in between

1 Solution

Accepted Solutions
15,373 Views
Registered: ‎03-02-2015

@yenigal

Hi,

I've already referred to the ug472 document.But in gui when i was selecting 156.25 MHz as the 3rd output clock,expected was around 149.xx.(error of 6-7 MHz)

Now,i tried to generate 156.25 MHz from 1st o/p clock which it is giving with no error.

If i try to generate 156.25 MHz from 2nd o/p clock,then i'm getting error of 0.25 MHz.

If i try to generate 156.25 MHz from 3rd o/p clock,then i'm getting error of 6-7 MHz.

If i try to generate from 4th o/p clock,error will probably be more.

This is from Clocking Wizard manual that as the number of o/p clock number increases,the accuracy may decrease.

2 Replies
Xilinx Employee
8,558 Views
Registered: ‎02-06-2013

Hi

Yes the frequencies of the output clocks you can generate  with an input reference clock depends on the input clock frequency,the output clock frequencies you want to generate and if this can be achieved by the VCO range and valid multiple and divide parameters .

Refer below doc for more details

http://www.xilinx.com/support/documentation/user_guides/ug472_7Series_Clocking.pdf

Regards,

Satish

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15,374 Views
Registered: ‎03-02-2015

@yenigal

Hi,

I've already referred to the ug472 document.But in gui when i was selecting 156.25 MHz as the 3rd output clock,expected was around 149.xx.(error of 6-7 MHz)

Now,i tried to generate 156.25 MHz from 1st o/p clock which it is giving with no error.

If i try to generate 156.25 MHz from 2nd o/p clock,then i'm getting error of 0.25 MHz.

If i try to generate 156.25 MHz from 3rd o/p clock,then i'm getting error of 6-7 MHz.

If i try to generate from 4th o/p clock,error will probably be more.

This is from Clocking Wizard manual that as the number of o/p clock number increases,the accuracy may decrease.