...
Anchor
Appendix C explains several differences between the two real-time kernels. However, access to µC/OS-II and µC/OS-III source files best highlights the differences.Anchor
Table C-1 is a feature-comparison chart for µC/OS-II and µC/OS-III.Anchor
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...
Feature |
...
µC/OS-II |
...
µC/OS-III |
...
...
Year of introduction |
...
1998 |
...
2009 |
...
...
Book |
...
...
Yes |
...
Yes |
...
...
Source code available |
...
Yes |
...
Yes |
...
...
Preemptive Multitasking |
...
...
Yes |
...
Yes |
...
...
Maximum number of tasks |
...
...
255 |
...
Unlimited |
...
...
Number of tasks at each priority level |
...
1 |
...
Unlimited |
...
...
Round Robin Scheduling |
...
...
No |
...
Yes |
...
Semaphores |
...
...
Yes |
...
Yes |
...
Mutual Exclusion Semaphores |
...
Yes |
...
...
Yes (nestable) |
...
...
Event Flags |
...
Yes |
...
Yes |
...
...
Message Mailboxes |
...
Yes |
...
No (not needed) |
...
Message Queues |
...
Yes |
...
...
Yes |
...
...
Fixed Sized Memory Management |
...
Yes |
...
Yes |
...
...
Signal a task without requiring a semaphore |
...
No |
...
Yes |
...
Send messages to a task without requiring a message queue |
...
No |
...
...
Yes |
...
...
Software Timers |
...
Yes |
...
Yes |
...
...
Task suspend/resume |
...
Yes |
...
Yes (nestable) |
...
Deadlock prevention |
...
Yes |
...
...
Yes |
...
...
Scalable |
...
Yes |
...
Yes |
...
Code Footprint |
...
...
6K to 26K |
...
6K to 24K |
...
Data Footprint |
...
...
1K+ |
...
...
1K+ |
...
...
ROMable |
...
Yes |
...
...
Yes |
...
...
Run-time configurable |
...
No |
...
Yes |
...
Catch a task that returns |
...
...
No |
...
...
Yes |
...
...
Compile-time configurable |
...
Yes |
...
...
Yes |
...
...
ASCII names for each kernel object |
...
Yes |
...
Yes |
...
Optio to post without scheduling |
...
...
No |
...
...
Yes |
...
...
Pend on multiple objects |
...
Yes |
...
...
Yes |
...
...
Task registers |
...
Yes |
...
Yes |
...
Built-in performance measurements |
...
...
Limited |
...
...
Extensive |
...
...
User definable hook functions |
...
Yes |
...
...
Yes |
...
...
Time stamps on posts |
...
No |
...
Yes |
...
...
Built-in Kernel Awareness support |
...
...
Yes |
...
...
Yes |
...
...
Optimizable Scheduler in assembly language |
...
No |
...
Yes |
...
...
Tick handling at task level |
...
No |
...
Yes |
...
Number of services |
...
...
~90 |
...
...
~70 |
...
...
MISRA-C:1998 |
...
Yes |
...
N/A |
...
...
MISRA-C:2004 |
...
No |
...
Yes |
...
DO178B Level A and EUROCAE ED-12B |
...
...
Yes |
...
...
In progress |
...
...
Medical FDA pre-market notification (510(k)) and pre-market approval (PMA) |
...
Yes |
...
...
In progress |
...
...
SIL3/SIL4 IEC for transportation and nuclear systems |
...
Yes |
...
In progress |
...
IEC-61508 |
...
...
Yes |
...
...
In progress |
...
Table C-1 µC/OS-II and µC/OS-III features comparison chart