Description STM32F405xx, STM32F407xx
18/167 Doc ID 022152 Rev 2
from TIMxCLK up to 84 MHz.
2. The camera interface is available only on STM32F407xxdevices.
2.2.1 ARM
®
Cortex™-M4F core with embedded Flash and SRAM
The ARM Cortex-M4F 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 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-M4F 32-bit RISC processor 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 STM32F40x family.
Note: Cortex-M4F 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™-M4F processors. It balances the inherent performance advantage
of the ARM Cortex-M4F 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.
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