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.

Figure 1. Random number generator

Page-1 Class.98 Sheet.99 Sheet.100 Sheet.101 Sheet.102 Sheet.103 Random number generator Random number generator Sheet.1 Sheet.2 Sheet.3 Sheet.4 Sheet.5 START START Sheet.6 STOP STOP Sheet.7 VALRDY VALRDY Sheet.8 VALUE VALUE

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.

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.

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.

Registers

Instances

Instance Base address Description
RNG 0x4000D000

Random number generator

Register overview

Register 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

TASKS_START

Address offset: 0x000

Task starting the random number generator

Bit number 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ID A
Reset 0x00000000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

W

TASKS_START

Task starting the random number generator

Trigger

1

Trigger task

TASKS_STOP

Address offset: 0x004

Task stopping the random number generator

Bit number 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ID A
Reset 0x00000000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

W

TASKS_STOP

Task stopping the random number generator

Trigger

1

Trigger task

EVENTS_VALRDY

Address offset: 0x100

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

Bit number 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ID A
Reset 0x00000000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

RW

EVENTS_VALRDY

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

NotGenerated

0

Event not generated

Generated

1

Event generated

SHORTS

Address offset: 0x200

Shortcuts between local events and tasks

Bit number 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ID A
Reset 0x00000000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

RW

VALRDY_STOP

Shortcut between event VALRDY and task STOP

Disabled

0

Disable shortcut

Enabled

1

Enable shortcut

INTENSET

Address offset: 0x304

Enable interrupt

Bit number 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ID A
Reset 0x00000000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

RW

VALRDY

Write '1' to enable interrupt for event VALRDY

Set

1

Enable

Disabled

0

Read: Disabled

Enabled

1

Read: Enabled

INTENCLR

Address offset: 0x308

Disable interrupt

Bit number 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ID A
Reset 0x00000000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

RW

VALRDY

Write '1' to disable interrupt for event VALRDY

Clear

1

Disable

Disabled

0

Read: Disabled

Enabled

1

Read: Enabled

CONFIG

Address offset: 0x504

Configuration register

Bit number 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ID A
Reset 0x00000000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

RW

DERCEN

Bias correction

Disabled

0

Disabled

Enabled

1

Enabled

VALUE

Address offset: 0x508

Output random number

Bit number 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ID A A A A A A A A
Reset 0x00000000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ID R/W Field Value ID Value Description
A

R

VALUE

[0..255]

Generated random number

Electrical specification

RNG Electrical Specification

Symbol Description Min. Typ. Max. Units
tRNG,START

Time from setting the START task to generation begins. This is a one-time delay on START signal and does not apply between samples.

 128 µs
tRNG,RAW

Run time per byte without bias correction. Uniform distribution of 0 and 1 is not guaranteed.

 30 µs
tRNG,BC

Run time per byte with bias correction. Uniform distribution of 0 and 1 is guaranteed. Time to generate a byte cannot be guaranteed.

 120 µs