Timing Parameters and Concepts

Gate delay

The time between a 50% transition on the input to a 50% transition on the output.

It is also called as propagation delay ‘tp’.

•         Tpl2h – time to propagate low on input to high on output

•         Tph2l – time to propagate high on input to low on output

 

 

Slope

The time difference between the 20% and 80% transition on a signal. It is also known as trasition delay, wave delay.

·         SlopeL2H – Slope for a low to high transition

·         SlopeH2L – Slope for a high to low transition

Some tools use different definitions

·         Tool reports 0%-100%, measures 10%-90%

·         Most tools use 20%-80%

 

 

 

 

Clock

•         Reference clock (virtual clock, system clock) is an ideal periodic signal that serves as a common reference for all timing events. It has the following properties: Rise time, Fall time, Period. Multiple reference clocks with different frequencies may exist in the same design

•         Qualified clock is an actual circuit signal with constant relation to some reference clock. Clocks are the controlling signal of sampling/generating elements