STM32F405 datasheet(20/204 Pages) STMICROELECTRONICS

20 / 204 page

Description

STM32F405xx, STM32F407xx

20/203

DS8626 Rev 9

2.2.1

Arm® Cortex®-M4 core with FPU and embedded Flash and SRAM

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

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

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

delivering outstanding computational performance and an advanced response to interrupts.

The Arm Cortex-M4 32-bit RISC processor with FPU features exceptional code-efficiency,

delivering the high-performance expected from an Arm core in the memory size usually

associated with 8- and 16-bit devices.

The processor supports a set of DSP instructions which allow efficient signal processing and

complex algorithm execution.

Its single precision FPU (floating point unit) speeds up software development by using

metalanguage development tools, while avoiding saturation.

The STM32F405xx and STM32F407xx family is compatible with all Arm tools and software.

Figure 5 shows the general block diagram of the STM32F40xxx family.

Note:

Cortex-M4 with FPU is binary compatible with Cortex-M3.

2.2.2

Adaptive real-time memory accelerator (ART Accelerator)

The ART Accelerator is a memory accelerator which is optimized for STM32 industry-

standard Arm® Cortex®-M4 with FPU processors. It balances the inherent performance

advantage of the Arm Cortex-M4 with FPU over Flash memory technologies, which normally

requires the processor to wait for the Flash memory at higher frequencies.

To release the processor full 210 DMIPS performance at this frequency, the accelerator

implements an instruction prefetch queue and branch cache, which increases program

execution speed from the 128-bit Flash memory. Based on CoreMark benchmark, the

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

execution from Flash memory at a CPU frequency up to 168 MHz.

2.2.3

Memory protection unit

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

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

task. This memory area is organized into up to 8 protected areas that can in turn be divided

up into 8 subareas. The protection area sizes are 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.

2.2.4

Embedded Flash memory

The STM32F40xxx devices embed a Flash memory of 512 Kbytes or 1 Mbytes available for

storing programs and data, plus 512 bytes of OTP memory.

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