Abassi RTOS for 8051/8052

Download it here

Available as freeware with most features enabled or with few features enabled for a small code size. It is without resrictions, time limits or commercial use limitations.


    1. Fully scalable footprint (as low as 3800 bytes on 8051/8052; full: ~12900 bytes)
    2. Fast Execution
    3. Unlimited Tasks, Queues, Events, Semaphores, Mutexes and Mailboxes
    4. Flexible licensing options
    5. Available source code
    6. Comprehensive documentation
    7. Responsive Technical Support

Unmatched Feature Set

In addition to the standard feature set supported by most real-time kernels, the Abassi RTOS can be configured with many features unmatched in the industry. These features add robustness and code savings, and include:

    1. Intelligent starvation protectionGuarantees fair access to CPU, via enhanced priority aging, even on heavily loaded systems.
    2. Priority inheritance, including dynamic trackingAutomatically adjusts for priority aging, timeouts, etc. and propagationBetween entangled mutex owners, to prevent deadlock.
    3. Adaptive priority ceiling
    4. Deadlock detectionReports recursive mutex dependencies anywhere in the execution chain.
    5. AsymmetricTimeslice adjustable at a per task level. Round Robin scheduling
    6. Hybrid interrupt stack

Development Tool Choices

Abassi supports major 8051/8052 development tools, including Keil/C51.

Memory Requirements

Don't settle for half a RTOS! Even with all features enabled, Abassi still consumes less memory than the minimum configuration of most kernels. And you get advanced priority inheritance, asymmetric round-robin scheduling, starvation protection, and much more. Or, if memory footprint is paramount, Abassi scales to a minimum size that can't be matched.

"C" Code Memory Usage
Description Size
Minimal Build
+ Runtime service creation / static memory
<3250 bytes
+ Multiple tasks at same priority <4000 bytes
+ Runtime priority change
+ Mutex priority inheritance
+ Task suspension
<6050 bytes
+ Timer & timeout
+ Timer call back
+ Round robin
<8100 bytes
+ Events
+ Mailbox
<11000 bytes
Full Feature Build (no names) <12350 bytes
Assembly Code Memory Usage
Description Size
Assembly code size 553 bytes
Fast Interrupts Enabled +94 bytes
Data Memory Usage
Description Size
Base Kernel 41 bytes
+ Task 22 bytes
+ Semaphore 8 bytes
+ Request 9 bytes
+ Mailbox 17 bytes
Measured using current software release, configured for 8052 at 11.0592 MHz and Keil μVision, Version 4.10

For your exact data memory requirements, please consult the Porting Document that applies to your design environment.

Kernel Snapshot

  1. Fully preemptive
  2. Scalable
  3. Very small code and data footprint
  4. Code can reside in ROM
  5. Zero interrupt latency kernel
  6. Mutexes
    1. Configurable priority inheritance
    2. Adaptive priority ceiling
    3. Priority based and first-come, first-served
  7. Versatile semaphores
    1. Counting and binary
    2. Priority based and first-come, first-served
  8. Mailboxes
    1. Priority based and first-come, first-served
  9. Events
  10. Intelligent starvation protection
  11. Hybrid interrupt stack
  12. Deadlock detection
  13. Single or multiple tasks per priority level
  14. Configurable Round Robin
  15. Dynamic priority changes
  16. Compile time task and component creation
  17. Run-time safe service creation
  18. No fixed number of tasks or components
  19. Programmable timeout on components
  20. Selectable scheduling search algorithm
  21. Optional cooperative mode
  22. Debug logging