Express Logic Offers Embedded Memory Protection for ThreadX RTOS

4/5/2004 - Express Logic, Inc., the worldwide leader in royalty-free real-time operating systems (RTOS) with over 100 million deployments, announced the introduction of Embedded Memory ProtectionTM (EMP) support for embedded applications using its flagship ThreadX® RTOS. Now, for the first time, developers can benefit from the memory protection capabilities of the MMU built into many embedded processors without the overhead and complexity of desktop-style implementations.

The Benefits
EMP enables developers to set up “watertight compartments” around threads, preventing bugs in those threads from damaging other threads or the ThreadX kernel. During development, this compartmentalization can help identify bugs that otherwise might go undetected until a problem appeared in some other thread. Such bugs are among the most difficult to identify, but EMP automatically traps them and informs the developer immediately. In production, EMP can help contain the damage done by bugs that escaped testing prior to shipment, and enable a fail-soft mode to be entered, keeping the product “afloat” with reduced functionality until repairs can be made.

How It Differs
Unlike other memory protection approaches that involve virtual memory and a process model, Express Logic’s EMP features a simplified design, low overhead and ease of use. EMP is an optional capability of the ThreadX RTOS that can easily be activated or deactivated for full development flexibility. Existing ThreadX applications can continue to operate without EMP, which is fully compatible with previous releases. For more details on how EMP differs from traditional virtual memory approaches, see the attached EMP Backgrounder.

A Peek Under The Hood
Express Logic’s EMP is implemented as a set of simple function calls for ThreadX, extending the ThreadX API, while retaining compatibility with existing code. EMP maps all program memory (“logical memory”) directly, page-by-page, to physical memory. Thus, a unified single address space is retained and consistent for all threads. EMP enables a thread to set boundaries around regions of its memory and to permit only specified access (READ_ONLY, READ_WRITE, NO_ACCESS) to those regions. This feature prevents bugs in the thread from causing unintended code or data access, which could overwrite the code or data of other threads or the kernel. While it is extremely small and efficient, EMP may be turned on or off easily, enabling it to be configured by the developer for maximum utility during development and then turned off for production shipments, yielding the smallest, fastest software possible for deployment, and avoiding any increase in memory size, cost, and power consumption.

About ThreadX
Express Logic’s ThreadX real-time operating system is a small, fast, royalty-free RTOS designed for embedded applications that demand small memory footprint, high efficiency, and low cost. ThreadX boasts extremely small memory requirements as well as very high performance. ThreadX also provides many advanced features, including a picokernelTM architecture, preemption-thresholdTM, optimized software timers, and priority inheritance. ThreadX has been deployed in over 100 million electronic products since 2001, making it one of the most widely deployed RTOSs in the world.

About Express Logic and ThreadX
Headquartered in San Diego, CA, Express Logic offers the most advanced run-time solution for deeply embedded applications, including the popular ThreadX RTOS, the high-performance TCP/IP stack NetXTM, and the embedded MS-DOS file system FileXTM. All products from Express Logic include full source-code and have no run-time royalties. For more information about Express Logic solutions, please browse to, call 1-888-THREADX, or email inquires to

ThreadX is a registered trademark of Express Logic, Inc. EMP, NetX, FileX, CANX, preemption-threshold, picokernel, UDP fast path technology, are trademarks of Express Logic, Inc.

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