STM32L4R9AI datasheet(18/306 Pages) STMICROELECTRONICS

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Functional overview

STM32L4R5xx, STM32L4R7xx and STM32L4R9xx

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DocID030321 Rev 3

Functional overview

3.1

Arm® Cortex®-M4 core with FPU

The Arm® Cortex®-M4 with FPU processor is the latest generation of Arm® processors for

embedded systems. It was developed to provide a low-cost platform that meets the needs of

the MCU implementation, with a reduced pin count and with low-power consumption, while

delivering outstanding computational performance and an advanced response to interrupts.

The Arm® Cortex®-M4 with FPU 32-bit RISC processor features an exceptional code-

efficiency, delivering the expected high-performance from an Arm® core in a memory size

usually associated with 8-bit and 16-bit devices.

The processor supports a set of DSP instructions which allows an efficient signal processing

and a complex algorithm execution. Its single precision FPU speeds up the software

development by using metalanguage development tools to avoid saturation.

With its embedded Arm® core, the STM32L4Rxxx family is compatible with all Arm® tools

and software.

Figure 1 shows the general block diagram of the STM32L4Rxxx family devices.

3.2

Adaptive real-time memory accelerator (ART Accelerator™)

The ART Accelerator™ is a memory accelerator that is optimized for the STM32 industry-

standard Arm®Cortex®-M4 processors. It balances the inherent performance advantage of

the Arm® Cortex®-M4 over Flash memory technologies, which normally requires the

processor to wait for the Flash memory at higher frequencies.

To release the processor near 150 DMIPS performance at 120 MHz, the accelerator

implements an instruction prefetch queue and a branch cache, which increases the

program’s execution speed from the Flash memory. Based on CoreMark benchmark, the

performance achieved thanks to the ART accelerator is equivalent to 0 wait state program

execution from the Flash memory at a CPU frequency of up to 120 MHz.

3.3

Memory protection unit

The memory protection unit (MPU) is used to manage the CPU accesses to the memory

and to prevent one task to accidentally corrupt the memory or the resources used by any

other active task. This memory area is organized into up to eight protected areas, which can

be divided in up into eight subareas each. The protection area sizes range between 32

bytes and the whole 4 gigabytes of addressable memory.

The MPU is especially helpful for applications where some critical or certified code has to be

protected against the misbehavior of other tasks. It is usually managed by an RTOS (real-

time operating system). If a program accesses a memory location that is prohibited by the

MPU, the RTOS can detect it and take action. In an RTOS environment, the kernel can

dynamically update the MPU area setting based on the process to be executed.

The MPU is optional and can be bypassed for applications that do not need it.

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