DELAY_VALUE Attribute

UltraScale Architecture SelectIO Resources User Guide (UG571)

Document ID
UG571
Release Date
2022-08-31
Revision
1.14 English

When the DELAY_FORMAT attribute is set to TIME mode, the DELAY_VALUE attribute represents time in ps. Unlike IDELAYE3, the ODELAYE3 has no clock/data align delay. The total delay through the ODELAYE3 is thus the value of the DELAY_VALUE.

In TIME mode, the DELAY_VALUE represents time in ps, but the value read or written from or to the delay line by the CNTVALUEIN[8:0] and/or CNTVALUEOU[8:0] is expressed in taps. So changing the time of a delay line requires some calculation, which is provided in the DELAY_MODE/VAR_LOAD paragraph. When the DELAY_FORMAT attribute is set to COUNT mode, the DELAY_VALUE attribute represents an amount of taps.

 

TIP:   When using delay lines in COUNT mode, the EN_VTC pin must be deasserted (Low). When using delay lines in TIME mode, the EN_VTC pin must be asserted (High) while IDELAYCTRL.RDY is Low. It can optionally be deasserted after RDY goes High.