DescriptionQ992
Q992DesignMetaASIC interview problem
Maximum clock frequency from a setup path
TechniquesTimingSTASetupClock skew
DifficultyMedium
TopicTiming
LanguagePython
Requirements4 checkpoints
01
Problem
For each setup path, positive skew means the capture clock arrives after the launch clock. Calculate the minimum clock period and maximum frequency using the given picosecond delays and uncertainty.
Starting declarationPython
Tmin = Tcq + Tcomb + Tsetup + uncertainty - capture_skew
Fmax_GHz = 1000 / Tmin_ps
P1 = (80, 620, 100, 60, 40)
P2 = (70, 500, 80, 50, 0)
P3 = (90, 700, 110, 40, -30)
// tuple order: Tcq,Tcomb,Tsetup,uncertainty,capture_skewExample input and output
Use this case to check your interpretationInput
P3: Tcq=90, Tcomb=700, Tsetup=110, uncertainty=40, capture_skew=-30 psOutput
Tmin=970 ps; Fmax=1.031 GHzExplanation
Subtracting -30 adds 30 ps to the requirement: 90+700+110+40+30=970 ps.
02
Requirements (4)
- Apply the formula independently to each path.
- Treat negative capture skew as additional required period because the formula subtracts it.
- Keep every delay in picoseconds and report frequency in GHz.
- Report period as integer picoseconds and frequency rounded to three decimals.