µC/OS RTOS Features Comparison

Which real-time kernel should you use?
Micrium's kernels meet different needs.

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 ✔ ✔