Dynamic Tick Mode is a power-saving feature that was first introduced in μC/OS-III V3.05.00 and later revised in µC/OS-III V3.07.00. It is a compromise between the approaches outlined in the sections on Tickless Mode and Periodic Tick Mode in that it gives low power applications the option to utilize timing services, without the drawback of waking the system up periodically.

Implications

• The full set of time services is available for use.
• Round-robin scheduling cannot be used in this mode. A build error will be generated if both features are enabled.

Requirements

Dynamic Tick requires a hardware timer which features:

• An up-counting (or down-counting) mode
• A programmable ceiling (or floor) value which:
  • Generates an interrupt on match
  • Sets a status bit on match
• A counter that can be read while the timer is running
• A frequency that is an integer multiple of the OS Tick rate

There are also non-essential timer characteristics which ensure that Dynamic Tick works optimally in your system.

• The timer frequency should be equal to the OS Tick frequency.
• The register width of the timer should match the size of the OS_TICK type (32-bit by default).

Dynamic Tick

As demonstrated below, the system behavior changes drastically while using dynamic tick.