Improving the Performance of Execution Time Control by Using a Hardware Time Management Unit

Execution time timers for interrupt handling

“…Test results are given for the implementation with and without the TMU [6,7], to show the interrupt handler overhead caused by implementing execution time control for interrupts as seen in Figure 1. Testing of the TMU was done by simulation as it has not yet been included in a produced UC3 chip.…”

“…Two implementations of execution time control exists for GNATforAVR32: a standard implementation using the COUNT / COMPARE registers of the AVR32 [6], and a hardware accelerated implementation using the Time Management Unit (TMU) [7]. The two implementations share the base design, and only differ in the low-level code interfacing to the hardware timers.…”

“…Low additional overhead for interrupt handling is important for these features to be acceptable in real-time systems. Therefore the Time Management Unit (TMU), a hardware timer specialized for execution time control was designed [7], and later implemented for the AVR32 architecture [12]. Testing with GNATforAVR32 showed that the TMU reduced the overhead of execution time control significantly [7].…”

“…Therefore the Time Management Unit (TMU), a hardware timer specialized for execution time control was designed [7], and later implemented for the AVR32 architecture [12]. Testing with GNATforAVR32 showed that the TMU reduced the overhead of execution time control significantly [7]. This paper is organized as follows: Section 2 describes the additions needed to the Ada 2012 standard for supporting interrupt timers; Section 3 gives a summary of the two implementations for GNATforAVR32 and test results for these; Section 4 describes how the object-oriented real-time framework can be extended to use interrupt timers, and an example application is given; Section 5 discusses the usefulness of interrupt timer features, the API changes, its possible implementation and overhead; and finally Section 6 gives the conclusions.…”

An extended ravenscar profile for execution time control

“…The implementation cost and run-time overhead of timers is moderate, and can be further reduced by using specialized hardware timers [11]. The feature has already been included in otherwise Ravenscar compliant run-time environments [5,10,13].…”