FIXED Mode

UltraScale Architecture SelectIO Resources User Guide (UG571)

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

The DELAY_TYPE attribute set to FIXED selects the fixed delay through the output delay line and is determined by the DELAY_VALUE and DELAY_FORMAT attribute. When the DELAY_FORMAT is set to TIME, the value loaded in the delay line is in ps. When the DELAY_FORMAT is set to COUNT, the delay value loaded in the delay line is the number of taps. During the reset sequence, RXTX_EN_VTC is kept High by the High-Speed SelectIO wizard. After the reset sequence has finished, the RXTX_EN_VTC should be controlled based on the DELAY_FORMAT setting.

When DELAY_FORMAT is TIME, then RXTX_BITSLICE.EN_VTC must be pulled High so that the delay automatically changes the number of taps over voltage and temperature to ensure the delay stays at the requested time in ps.

With DELAY_FORMAT set to COUNT, RXTX_BITSLICE.EN_VTC must be Low in Count mode. Then the delay is not compensated for voltage and temperature.