Feature |
µC/OS-II |
µC/OS-III |
Release Date |
1999–present |
2009–present |
Preemptive Multitasking |
✔ |
✔ |
Maximum number of tasks |
255 |
Unlimited |
Number of tasks at each priority level |
1 |
Unlimited |
Round robin scheduling |
|
✔ |
Semaphores |
✔ |
✔ |
Mutual exclusion semaphores |
✔ |
✔ (Nestable) |
Event flags |
✔ |
✔ |
Message mailboxes |
✔ |
No (not needed) |
Message queues |
✔ |
✔ |
Fixed sized memory management |
✔ |
✔ |
Signal a task without requiring a semaphore |
|
✔ |
Option to post without scheduling |
|
✔ |
Send messages to a task without requiring a message queue |
|
✔ |
Software timers |
✔ |
✔ |
Task suspend/resume |
✔ |
✔ (Nestable) |
Deadlock prevention |
✔ |
✔ |
Scalable |
✔ |
✔ |
Code footprint |
6K to 26K |
6K to 24K |
Data footprint |
1K+ |
1K+ |
ROMable |
✔ |
✔ |
Run-time configurable |
|
✔ |
Compile-time configurable |
✔ |
✔ |
ASCII names for each kernel object |
✔ |
✔ |
Pend on multiple objects |
✔ |
✔ |
Task registers |
✔ |
✔ |
Built-in performance measurements |
Limited |
Extensive |
User definable hook functions |
✔ |
✔ |
Time stamps on posts |
|
✔ |
Built-in kernel awareness support |
✔ |
✔ |
Optimizable scheduler in assembly language |
|
✔ |
Catch a task that returns |
|
✔ |
Tick handling at task level |
|
✔ |
Dynamic tick rate |
|
✔ |
Source code available |
✔ |
✔ |
Number of services |
~90 |
~70 |
MISRA-C:1998 |
✔ (except 10 rules) |
N/A |
MISRA-C:2012 |
|
✔ (except 8 advisory and 8 required guidelines) |
DO178B Level A and EUROCAE ED-12B |
✔ |
✔ |
Medical FDA pre-market notification (510(k)) and pre-market approval (PMA) |
✔ |
✔ |
SIL3/SIL4 IEC for transportation and nuclear systems |
✔ |
✔ |
IEC-61508 |
✔ |
✔ |
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