63.5 Functional Description

As soon as the TRNG is enabled in the Control register (TRNG_CR), the generator provides one 32-bit random value at a maximum streaming rate of 84 clock cycles. Entropy rate increases at a lower frequency. For a lower streaming rate, the software intervention is required to skip, on a regular basis, the data ready information reported in the Status register (TRNG_ISR).

The TRNG interrupt line can be enabled in the Interrupt Enable register (TRNG_IER), and disabled in the Interrupt Disable register (TRNG_IDR). This interrupt is set when a new random value is available and is cleared when the Status register (TRNG_ISR) is read. The flag TRNG_ISR.DATRDY is set when the random data is ready to be read out on the 32-bit Output Data register (TRNG_ODATA).

The normal operating mode checks that the TRNG_ISR.DATRDY flag equals ‘1’ before reading TRNG_ODATA when a 32-bit random value is required by the software application.