The tap size of the ODELAYE3 primitive is defined in the UltraScale device data sheets as TODELAY_RESOLUTION (TIDELAY_RESOLUTION for IDELAYE3). If the DELAY_FORMAT is set to TIME, the delay line is calibrated, controlled, and maintained for voltage and temperature by the IDELAYCTRL component.
- An IDELAYCTRL component must be used.
- The REFCLK_FREQUENCY attribute must reflect the clock frequency applied to the IDELAYCTRL component.
- The EN_VTC pin must be actively manipulated when the delay line is used in VARIABLE or VAR_LOAD mode. When FIXED mode is used, tie the EN_VTC pin High.
When the DELAY_FORMAT is set to COUNT, the delay line is not calibrated and is not maintained over voltage and temperature. Therefore:
- Do not use an IDELAYCTRL component.
- Leave the REFCLK_FREQUENCY attribute at the default value (300 MHz).
- Tie the EN_VTC input pin Low.
- This pin ensures that calibration and VT maintenance logic in the ODELAYE3 is disabled.
- The delay line must be used to represent an amount
of taps.
- It does not matter how long the tap delay is; it is the amount of taps that is important.
- 512 taps are available.
- The CNTVALUEIN/OUT[8:0] values represent the amount of taps the delay line is set or tuned to.
Examples of how the DELAY_FORMAT attribute is used are provided in the mode paragraphs in the DELAY_VALUE Attribute.