Characterization and functional test in a processor or system utilizing critical path monitor to dynamically manage operational timing margin

Abstract

Guardband validation for a device having a critical path monitor involves first applying multiple calibration settings to the monitor during functional operation of the processor, and recording corresponding guardbands which result in reduced timing margin. A desired guardband can later be selected for validation. The calibration settings can be based on delays for a critical path. A calibration test procedure can be used to determine the calibration delays for different operating frequencies or voltages that are set or, alternatively, the calibration delays can be set and resultant frequencies measured which are used to calculate the guardband amounts. The critical path monitor may include a modified calibration delay circuit which provides a calibrated delay signal to a critical path synthesis circuit, and the multiple calibration settings can be applied by changing delay taps of the calibration delay circuit in response to a bias delay signal from a power management controller.