NRF52820-QDAA-R datasheet(227/437 Pages) NORDIC

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Peripherals

6.13 RNG — Random number generator

The Random number generator (RNG) generates true non-deterministic random numbers based on

internal thermal noise that are suitable for cryptographic purposes. The RNG does not require a seed

value.

Random number

generator

START

STOP

VALRDY

VALUE

Figure 79: Random number generator

The RNG is started by triggering the START task and stopped by triggering the STOP task. When started,

new random numbers are generated continuously and written to the VALUE register when ready. A

VALRDY event is generated for every new random number that is written to the VALUE register. This means

that after a VALRDY event is generated, the CPU has the time until the next VALRDY event to read out the

random number from the VALUE register before it is overwritten by a new random number.

6.13.1 Bias correction

A bias correction algorithm is employed on the internal bit stream to remove any bias toward

1 or 0. The

bits are then queued into an eight-bit register for parallel readout from the VALUE register.

It is possible to enable bias correction in the CONFIG register. This will result in slower value generation,

but will ensure a statistically uniform distribution of the random values.

6.13.2 Speed

The time needed to generate one random byte of data is unpredictable, and may vary from one byte to

the next. This is especially true when bias correction is enabled.

6.13.3 Registers

Base address

Peripheral

Instance

Description

Configuration

0x4000D000

RNG

Random number generator

Table 64: Instances

Offset

Description

TASKS_START

0x000

Task starting the random number generator

TASKS_STOP

0x004

Task stopping the random number generator

EVENTS_VALRDY

0x100

Event being generated for every new random number written to the VALUE register

SHORTS

0x200

Shortcuts between local events and tasks

INTENSET

0x304

Enable interrupt

INTENCLR

0x308

Disable interrupt

CONFIG

0x504

Configuration register

VALUE

0x508

Output random number

Table 65: Register overview

6.13.3.1 TASKS_START

Address offset: 0x000

4463_156 v1.0

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