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lebowski
Explorer
Explorer
271 Views
Registered: ‎02-27-2018

How to use ODELAYE3 in VAR_LOAD mod? calculation of tap size and calculation of CNTVALUEIN

Hello,

I'm having problems understand how to use the ODELAYE3 in VAR_LOAD mode.

My goal is to delay a signal by a value of picoseconds stored in a register (GOALDELAY(ps))

I assume that i have to use the VAR_LOAD mode and use and IDELAYCTRL

1) How do we connect the IDELAYCTRL to ODELAYE3

2) I read in the answer record https://www.xilinx.com/support/answers/66013.html

that i have to determine the aligndelay by setting the DELAY_VALUE to 0 and reading CNTVALUEOUT

Is DELAY_VALUE the output delay tap setting?

(DELAY_VALUE => 0, -- Output delay tap setting)

Do the reset of IDELAYCTRL has to be at '1' during this phase? How about the the reset of ODELAYE3 and the signa EN_VTC?

It is said afterwards that i have to set DELAY_VALUE to a non fixed zero to calculate the tap size.

I don't understand how we can set twice the setting DELAY_VALUE ? since it is not a signal but a parameter.

 

Thanks for your help

 

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1 Reply
panantra
Xilinx Employee
Xilinx Employee
162 Views
Registered: ‎06-13-2018

Hi  @lebowski ,

I assume that i have to use the VAR_LOAD mode and use and IDELAYCTRL
-- If you are using ODELAYE3 in TIME mode, then you need to use IDELAYCTRL for US/US+ devices. If the DELAY_FORMAT is set to TIME, the delay line is calibrated, controlled, and maintained for voltage and temperature by the IDELAYCTRL component. This is not used for COUNT mode.


 How do we connect the IDELAYCTRL to ODELAYE3
-- You need to take care of RDY and REFCLK of IDELAYCTRL.
1. Release the IDELAY reset once RDY signal of IDELAYCTRL is asserted or use the complement of RDY as reset to IDELAY.
2. The REFCLK_FREQUENCY attribute of ODELAY must reflect the clock frequency applied to the IDELAYCTRL component. Refer 2-16 in UG 571 REFCLK_FREQUENCY section. Also, please follow reset sequence given in UG571, titled "Component Mode Reset Sequence" or you can refer to this AR: https://www.xilinx.com/support/answers/64198.html 


2) I read in the answer record https://www.xilinx.com/support/answers/66013.html
that i have to determine the aligndelay by setting the DELAY_VALUE to 0 and reading CNTVALUEOUT
-- For IDELAYE3 in TIME mode, we need to consider clock alignment delay. This is not applicable for ODELAYE3. 
Follow this AR https://www.xilinx.com/support/answers/60802.html for ODELAY calibration. You will find the procedure to calculate CNTVALUEIN under VAR_LOAD section.
 
Thanks,
Priyanka
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