The DELAY_TYPE attribute set to FIXED selects the delay through the IDELAYE3 primitive 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.
- When DELAY_FORMAT is TIME, then 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, EN_VTC must be Low. In COUNT mode, the delay is not compensated for voltage and temperature.