23.6.1.4 Voltage Scaling Control

The VDDCORE supply will change under certain circumstances:
  • When a new performance level (PL) is set
  • When the standby sleep mode is entered or left
  • When a sleepwalking task is requested in standby sleep mode

To prevent high peak current on the main power supply and to have a smooth transition of VDDCORE, both the voltage scaling step size and the voltage scaling frequency can be controlled: VDDCORE is changed by the selected step size of the selected period until the target voltage is reached.

The Voltage Scaling Voltage Step field is in the VREG register, VREG.VSVSTEP. The Voltage Scaling Period field is VREG.VSPER.

The following waveform shows an example of changing performance level from PL0 to PL2.

Setting VREG.VSVSTEP to the maximum value allows to transition in one voltage step.

The STATUS.VCORERDY bit is set to '1' as soon as the VDDCORE voltage has reached the target voltage. During voltage transition, STATUS.VCORERDY will read '0'. The Voltage Ready interrupt (VCORERDY) can be used to detect a 0-to-1 transition of STATUS.VCORERDY, see also Interrupts.

When entering the standby sleep mode and when no sleepwalking task is requested, the VDDCORE Voltage scaling control is not used.