NSS-30014: Asynchronous Pulse Generators

A pulse generator in a design should not generate pulses in any of the following ways:

  • Creating a wide glitch using a two-input AND, NAND, OR, or NOR gate, where the source for the two gate inputs are the same, but the design inverts the source for one of the gate inputs.
    Figure 1. Asynchronous Pulse Generator Example

  • Using a register where the register output drives the register's own asynchronous reset signal through a delay chain (one or more consecutive nodes that act as a buffer for creating intentional delay).
    Figure 2. Asynchronous Pulse Generator Example

These pulse generators are asynchronous, where the generated pulse width can never be reliably predefined. As a result, the pulse width depends on the circuit delay. For example, the pulse width generated by a pulse generator that uses a 2-input AND gate depends on the relative delays of the path that drives the AND gate directly and the path that the design inverts before driving the AND gate.


A pulse generator should generate pulses as shown in the following example image of a recommended pulse generator that is implemented in a synchronous manner:

Figure 3. Synchronous Pulse Generator




Analysis and Elaboration

Device Family

  • Intel® Arria® 10
  • Intel® Cyclone® 10 GX