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.