RM0090 Rev 18 767/1749
RM0090 Random number generator (RNG)
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24 Random number generator (RNG)
This section applies to the whole STM32F4xx family, unless otherwise specified.
24.1 RNG introduction
The RNG processor is a random number generator, based on a continuous analog noise,
that provides a random 32-bit value to the host when read.
The RNG passed the FIPS PUB 140-2 (2001 October 10) tests with a success ratio of 99%.
24.2 RNG main features
• It delivers 32-bit random numbers, produced by an analog generator
• 40 periods of the RNG_CLK clock signal between two consecutive random numbers
• Monitoring of the RNG entropy to flag abnormal behavior (generation of stable values,
or of a stable sequence of values)
• It can be disabled to reduce power consumption
24.3 RNG functional description
Figure 232 shows the RNG block diagram.
Figure 232. Block diagram
1. For more details about RNG Clock (RNG_CLK) source, please refer to Section 6: Reset and clock control
for STM32F42xxx and STM32F43xxx (RCC) and Section 7: Reset and clock control for
STM32F405xx/07xx and STM32F415xx/17xx(RCC).
The random number generator implements an analog circuit. This circuit generates seeds
that feed a linear feedback shift register (RNG_LFSR) in order to produce 32-bit random
numbers.
32-bit AHB bus
RNG_DR
RNG
_CR
RNG
_SR
Status register
Control register
fault detector
LFSR
Analog seed
RNG_CLK
Clock checker &
data register
Shift Register
feed a Linear Feedback
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