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14.4.2. Event-Based Timing Controls

Event-based timing controls use the @ symbol to detect signal transitions or changes. These are the ONLY timing controls that are synthesizable when used properly in RTL design.

14.4.2.1 Edge-Sensitive Event Controls

posedge (Positive Edge)

Triggers when signal transitions from 0 to 1 (or X to 1, Z to 1).

Verilog

negedge (Negative Edge)

Triggers when signal transitions from 1 to 0 (or X to 0, Z to 0).

Verilog

Edge Detection Transitions

Screenshot (749).png

14.4.2.2 Level-Sensitive Event Control (OR-ing Events)
 

Single Signal Change

Verilog

Multiple Signals (OR Sensitivity)

Verilog

Mixed Edge and Level Events

Verilog

14.4.2.3 Named Events
 

Named events provide a way to trigger execution without using signals.
 

Declaration and Triggering

Verilog

Practical Example

Verilog

Delay based timing control

Level sensitive timing control
 

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