Altera HardCopy II Clock Uncertainty Calculator - Manual (Page 7)

Altera Corporation 1–1
August 2007
Chapter 1. About HardCopy II
Clock Uncertainty Calculator
Introduction "Clock uncertainty" is the interval of confidence around the ideal clock
value, such that the measured value is always within the stated interval.
Common sources of clock uncertainty include clock jitter, duty cycle
distortion, and phase shift error. Due to these sources, clock uncertainty
must be factored in to guard against deep submicron effects that are not
explicitly reflected in the timing models. The HardCopy II Clock
Uncertainty Calculator
™ provides the clock uncertainty values for
HardCopy ® II devices based on PLL phase error, PLL jitter, I/O buffer,
clock network noise, and core noise. Therefore, timing constraints that
consider clock uncertainty are required for the HardCopy II devices. You
must prepare the clock uncertainty timing constraints before starting
HardCopy II migration.