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Technical Data

Description ARM7™/ARM9™ Cortex™-M
Defined Tasks Unlimited Unlimited
Active Tasks 250 max 250 max
Mailboxes Unlimited Unlimited
Semaphores Unlimited Unlimited
Mutexes Unlimited Unlimited
Signals / Events 16 per task 16 per task
User Timers Unlimited Unlimited
Code Space <4.2 Kbytes <4.0 Kbytes
RAM Space for Kernel 300 bytes +
80 bytes User Stack
300 bytes +
128 bytes Main Stack
RAM Space for a Task TaskStackSize + 52 bytes TaskStackSize + 52 bytes
RAM Space for a Mailbox MaxMessages * 4 + 16 bytes MaxMessages * 4 + 16 bytes
RAM Space for a Semaphore 8 bytes 8 bytes
RAM Space for a Mutex 12 bytes 12 bytes
RAM Space for a User Timer 8 bytes 8 bytes
Hardware Requirements One on-chip timer SysTick timer
User task priorities 1 - 254 1 - 254
Task switch time <5.3 µsec @ 60 MHz <2.6 µsec @ 72 MHz
Interrupt lockout time <2.7 µsec @ 60 MHz Not disabled by RTX


  • Unlimited means that the RTX kernel does not impose any limitations on the number. However, the available system memory resources limit the number of items you can create.
  • The default configuration of the RTX kernel allows 10 tasks and 10 user timers. It also disables stack checking by default.
  • In the RTX kernel, Event is simply another name for signal.
  • RAM requirements depend on the number of concurrently running tasks.
  • The code and RAM size was calculated for MicroLib runtime library.
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