Intel® Quartus® Prime Standard Edition User Guide: Timing Analyzer

ID 683068
Date 2/21/2024
Public
Document Table of Contents

1.1.5.1. Multicycle Clock Hold

The number of clock periods between the clock launch edge and the latch edge defines the setup relationship.

By default, the Timing Analyzer performs a single-cycle path analysis, which results in the hold relationship being equal to one clock period (launch edge – latch edge).When analyzing a path, the Timing Analyzer performs two hold checks. The first hold check determines that the data that launches from the current launch edge is not captured by the previous latch edge. The second hold check determines that the data that launches from the next launch edge is not captured by the current latch edge. The Timing Analyzer reports only the most restrictive hold check. The Timing Analyzer calculates the hold check by comparing launch and latch edges.

The calculation the Timing Analyzer performs to determine the hold check.

Figure 23. Hold Check
Tip: If a hold check overlaps a setup check, the hold check is ignored.

A start multicycle hold assignment modifies the launch edge of the destination clock by moving the latch edge the number of clock periods you specify to the right of the default launch edge. The following figure shows various values of the start multicycle hold (SMH) assignment and the resulting launch edge.

Figure 24. Start Multicycle Hold Values

An end multicycle hold assignment modifies the latch edge of the destination clock by moving the latch edge the specific number of clock periods to the left of the default latch edge. The following figure shows various values of the end multicycle hold (EMH) assignment and the resulting latch edge.

Figure 25. End Multicycle Hold Values

The following shows the hold relationship the Timing Analyzer reports for the negative hold relationship:

Figure 26. End Multicycle Hold Values the Timing Analyzer Reports