The Tool Desk
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What is ST’s free safety-design package for STM32-based IEC 61508 applications?
X-CUBE-STL is STMicroelectronics’ package for functional-safety development with compatible STM32 MCUs and MPUs. ST identifies IEC 61508:2010 SIL 2 and SIL 3 safety functions as its targets. It also names ISO 13849, IEC 62061 and IEC 61800 as standards users may target with compatible STM32 devices.
The package is listed as free of charge in ST’s functional-safety ecosystem. Compatibility is device-specific: check ST’s current X-CUBE-STL product and ecosystem information, as supported-device details can change.
What does X-CUBE-STL include?
ST’s X-CUBE-STL data brief, revision 5 dated May 2025, describes four core elements:
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- High-performance foundation line, ARM Cortex-M4 core with DSP and FPU, 512 Kbytes Flash, 180 MHz CPU, ART Accelerator, Dual QSPI
- On-board ST-LINK/V2-1 debugger/programmer with SWD connector
- Can be powered from USB
- Three LEDs, Two Push-buttons
- Support of wide choice of Integrated Development Environments (IDEs) including IAR, ARM Keil, GCC-based IDEs
- MCU safety manual: sets out conditions of use and provides examples for applying the device in a safety design.
- MCU FMEA: gives a qualitative analysis of failure modes and mitigations.
- FMEDA snapshot: reports failure rates under IEC 61508:2010 at the MCU and basic-function levels.
- X-CUBE-STL diagnostic library and supporting documentation: provides software diagnostics intended to detect random hardware failures in the CPU, SRAM and flash.
ST describes the library as delivered in object code and compiler independent. It says diagnostic coverage was verified using ST’s fault-injection methodology; that is ST’s verification description, not evidence of independent validation. The data brief says the library is compliant with the IEC 61508:2010 SC3 (SIL 3) development process and is “Certified by TÜV Rheinland.”
What STM32 arrangement does ST specify for SIL 2 and SIL 3?
ST’s May 2025 data brief specifies different MCU arrangements for the two IEC 61508 safety-function targets:
Rank #2
- Ultra-low-power with FPU ARM Cortex-M4 MCU 80 MHz with 1 Mbyte Flash, LCD, USB OTG, DFSDM
- On-board ST-LINK/V2-1 debugger/programmer with SWD connector
- Can be powered from USB
- Three LEDs, Two Push-buttons
- Support of wide choice of Integrated Development Environments (IDEs) including IAR, ARM Keil, GCC-based IDEs
| Safety-function target | MCU arrangement stated by ST | Source and qualification |
|---|---|---|
| SIL 2 | One STM32 MCU | ST X-CUBE-STL data brief, revision 5, May 2025; package guidance. |
| SIL 3 | Two STM32 MCUs in a 1oo2 scheme | ST X-CUBE-STL data brief, revision 5, May 2025; package guidance. |
These are the arrangements ST specifies for this package, not a universal rule for every safety architecture or every standard. In particular, do not read the SIL 3 guidance as saying that one MCU is sufficient for the stated X-CUBE-STL arrangement.
Is the STM32 safety package SIL 3 certified?
Be precise about what is certified. ST says the X-CUBE-STL library is TÜV Rheinland certified and describes its development process as compliant with IEC 61508:2010 SC3 (SIL 3). These statements concern the library and its development process, not an automatic certification of every system built with it.
Rank #3
- Experience the power of the ARM Cortex M4 with this STM32F411CEU6 Development Board, featuring a blazing fast 100Mhz frequency and zero-wait state access to 512KB ROM and 128KB RAM for seamless programming
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- Stay powered up and connected with the 3.3V-5V power input, 3.3V LDO with a maximum output current of 100mA, and a USB-C interface with built-in diode to prevent power backflow, along with high-speed and low-speed crystal oscillators for reliable performance
- Elevate your programming projects with the STM32F411CEU6 Development Board, featuring a SPI Flash for additional storage options, 12-bit ADC, 12-bit 5 S for accurate measurements, and 32.768K 6pF low-speed crystal oscillator for precise timing control
Does using X-CUBE-STL certify a product?
No. ST presents the package as support for developing a safety application and assembling information relevant to its assessment. The application developer remains responsible for following the safety manual’s conditions of use and addressing the complete application and system safety process. The library’s certification is not a certificate for the finished product.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How should you check whether a device and package fit?
- Identify the exact MCU or MPU. Confirm the part number against ST’s current supported-device listing rather than assuming support for an entire STM32 family.
- Check the package materials for that device. Review its safety manual, conditions of use, FMEA and FMEDA information, along with the library documentation.
- Check the intended standard and safety level. ST names IEC 61508:2010 SIL 2/SIL 3 as X-CUBE-STL targets and lists ISO 13849, IEC 62061 and IEC 61800 as other standards users may target with compatible STM32 devices.
- Design against the stated architecture conditions. For the package’s IEC 61508 guidance, account for one MCU for a SIL 2 safety function or two STM32 MCUs in a 1oo2 scheme for a SIL 3 safety function.
- Plan the application assessment separately. Treat the library and supporting documents as inputs to the safety case, not as a substitute for assessing and certifying the complete application.
ST’s functional-safety ecosystem also includes packages for other domains, including X-CUBE-CLASSB and STM8-SafeCLASSB for household-appliance Class B standards. Those address different standards and use cases; they are not interchangeable alternatives to X-CUBE-STL for the IEC 61508 question.
Rank #4
- STM32 STM32F401RE microcontroller Cortex-M4 in LQFP64 package
- 1 user LED shared with UNO 1 user and 1 reset push-button
- Board expansion connectors: Uno V3 ST morpho extension pin headers for full access to all STM32 I/Os
- On-board ST-LINK/V2-1 debugger/programmer with USB re-enumeration capability. Three different interfaces supported on USB: mass storage, Virtual COM port and debug port
- Comprehensive free software libraries and examples available with the STM32Cube MCU Package
Because the technical details above come from data brief revision 5 (May 2025), use ST’s current product and ecosystem information to verify device support and available package materials before basing a design on them.
Quick Recap
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- STM32F103C8T6 ARM STM32 minimum system development module.
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- The board lead to all the I/O resources.Download with SWD debug interface, which requires a minimum of 3 wires to complete debug a download task
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