BLUENRG-332VC datasheet(8/67 Pages) STMICROELECTRONICS

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2.3.5

Memory protection unit (MPU)

The MPU is used to manage accesses to memory to prevent one task from accidentally corrupting the memory

or resources used by any other active task. This memory area is organized into up to 8 protected areas. 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 settings, based on the process to be executed.

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

2.4

Security and safety

The BlueNRG-LPS contains many security blocks for the BLE and the host application.

It includes:

•

Flash read/write protection over accidental and intentional actions

•

As protection against potential hacker attacks, the SWD access can be disabled

•

Secure bootloader (refer to the dedicated application note AN5471)

•

Customer storage of the BLE keys

•

True random number generator (RNG)

•

Public key accelerator (PKA) including:

–

Modular arithmetic including exponentiation with maximum modulo size of 3136 bits

–

Elliptic curves over prime field scalar multiplication, ECDSA signature, ECDSA verification with

maximum modulo size of 521 bits

•

Cyclic redundancy check calculation unit (CRC)

2.5

RF subsystem

The BlueNRG-LPS embeds an ultra-low power radio, compliant with Bluetooth Low Energy (BLE) specification.

The BLE features 1 Mbps and 2 Mbps transfer rates as well as long range options (125 kbps, 500 kbps), supports

multiple roles simultaneously acting at the same time as Bluetooth Low Energy sensor and hub device.

The BLE protocol stack is implemented by an efficient system partitioned as follows:

•

Hardware part: BlueCore handling time critical and time consuming BLE protocol parts

•

Firmware part: Arm® Cortex-M0+ core handling non time critical BLE protocol parts

2.5.1

RF front-end block diagram

The RF front end is based on a direct modulation of the carrier in TX, and uses a low IF architecture in RX mode.

Thanks to an internal transformer with RF pins, the circuit directly interfaces the antenna (single ended

connection, impedance close to 50 Ω). The natural band pass behavior of the internal transformer simplifies

outside circuitry aimed at harmonic filtering and out of band interferer rejection.

In transmit mode, the maximum output power is user selectable through the programmable LDO voltage of the

power amplifier. A linearized, smoothed analog control offers a clean power ramp-up.

In receive mode the circuit can be used in standard high performance or in reduced power consumption (user

programmable). The automatic gain control (AGC) is able to reduce the chain gain at both RF and IF locations, for

an optimized interferer rejection. Thanks to the use of complex filtering and highly accurate I/Q architecture, high

sensitivity, and excellent linearity can be achieved.

BlueNRG-LPS

Security and safety

DS13819 - Rev 4

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