General-Purpose I/O User Guide: Agilex™ 5 FPGAs and SoCs

ID 813934
Date 10/07/2024
Public
Document Table of Contents

7.7.2. Delay Elements

The Quartus® Prime software does not automatically set delay elements to maximize slack in the I/O timing analysis. To close the timing or maximize slack, set the delay elements manually in the Quartus® Prime settings file (.qsf).
Table 63.  Delay Elements .qsf AssignmentsSpecify these assignments in the .qsf to access the delay elements.
Delay Element .qsf Assignment
Input Delay Element set_instance_assignment –to <PIN> -name INPUT_DELAY_CHAIN <0..63>
Output Delay Element set_instance_assignment –to <PIN> -name OUTPUT_DELAY_CHAIN <0..15>
Output Enable Delay Element set_instance_assignment –to <PIN> -name OE_DELAY_CHAIN <0..15>
The Agilex™ 5 FPGAs and SoCs Device Data Sheet provides information on delay chain specification and offset settings across fast and slow models.
  • Fast model—Specifies the delay value when the maximum delay chain offset setting is selected using the fastest process.
  • Slow model—Specifies the delay value when the maximum delay chain offset setting is selected using the slowest process within a specific speed grade.

For example, if you assign input delay chain setting to #10 using an Agilex™ 5 device with -1 speed grade:

  • Minimum delay value = 10 * delay specification for fast model / 63 = x ns
  • Maximum delay value = 10 * delay specification for -1V slow model / 63 = y ns

The input delay ranges from x ns to y ns when you select -1 device speed grade in your design.

Note: The IOE delay chains are not process, voltage and temperature (PVT) compensated, which means the delay chain value changes across PVT.