Agilex™ 7 SEU Mitigation User Guide

ID 683128
Date 9/20/2024
Public
Document Table of Contents

2.3.2. Priority Scrubbing

You can assign portions of the design as high priority sectors for internal scrubbing; the unassigned portions become low priority sectors. The Agilex™ 7 EDC circuitry detects and corrects errors that occur in the high priority sectors more frequently than the other sectors.

The EDC operation for the priority sectors and non-priority sectors run in parallel when priority scrubbing is enabled. The sectors in group 0 of both the priority sectors and non-priority sectors run the EDC process at time T0. This is followed by the EDC operation of sectors in group 1 of both the priority sectors and non-priority sectors at time T1, sectors in group 2 at time T2, followed by the sectors of the remaining group until the last available group. This corresponds to 1 complete cycle of the EDC process.

For an Agilex™ 7 device with a total of 30 sectors and the maximum number of sectors allowed to run EDC concurrently, Smax = 5, Quartus® Prime determines the number of groups for the priority sectors, GP and non-priority sectors, GN based on the number of priority sectors, P and non-priority sectors, N. Within GP, there is at most Smax-1 number of sectors allocated so that there is at least one sector slot left for the normal sector to run concurrently.

If P≤Smax-1, then GP = 1 and GN is determined by allocating N to the vacant sector slots. For example, P+N = 30, where P = 2 and N = 28, as shown on the left side of the following figure. Since P≤Smax-1, then GP = 1. Two sector slots are occupied by the priority sectors and three sector slots are occupied by the non-priority sectors. GN = 10, is determined by allocating N into three sector slots. The priority sectors only need one unit of time to complete the EDC process compared to the non-priority sectors which need 10 units of time.

If P>Smax-1, then GP and GN are determined by allocating P equally into Smax-1 and N to the last vacant sector slot. For example, P = 6 and N = 24 as shown on the right side of the following figure. Since P>Smax-1, then GP = 2 where the priority sectors are divided equally. Three sector slots are occupied by the priority sectors and two sector slots are occupied by the non-priority sectors, resulting in GN = 12. The priority sectors only need two units of time to complete the EDC process compared to the non-priority sectors which need 12 units of time.

With priority scrubbing, priority sectors undergo more frequent SEU detection and correction compared to non-priority scrubbing. This provides faster SEU detection and correction for critical design modules. The interval time for priority sectors is always the minimum interval that the Agilex™ 7 device is capable of, regardless of the user setting of the Minimum SEU Interval in Device and Pin Options. For example, the interval time for one priority sector is always 2160 microseconds regardless if the Minimum SEU Interval is set to 0 or 10000 microseconds.

A warning message is prompted in Quartus® Prime when P exceeds a certain threshold which causes the priority sectors to require a longer time to complete one cycle of EDC process compared to the non-priority sectors.

Figure 3. Priority Scrubbing