TRNG Errata?

[chriscowdery]

Hi All,

 We are experiencing an issue with the TRNG. Inside the driver, there is mention of a defect in function trng_ReadEntropy().

 /* Dummy read. Defect workaround. * TRNG could not clear ENT_VAL flag automatically, application * had to do a dummy reading operation for anyone TRNG register * to clear it firstly, then to read the RTENT0 to RTENT15 again */

We are finding that after 1 or more reads, the peripheral starts to behave inconsistently, and cannot be used.

Is the Errata documented anywhere?, does it apply to the iMXRT1021?

Thanks,

Chris.

[jingpan]

Hi Chris,

there is a TRNG example in SDK. Have you tried it? It read 10 RNG data continuously. It hasn't any problem.

Regards,

Jing

[chriscowdery]

Hi,

 We found the default Frequency Count Limit was too low, so it was tripping its own error detection.

So it is resolved now.

Regards,

Chris.

[np]

Hi Chris,

May I please ask what you changed the Frequency Count Limit to? The default range in fsl_trng.c seems to be:

#define TRNG_USER_CONFIG_DEFAULT_FREQUENCY_MAXIMUM 25600
#define TRNG_USER_CONFIG_DEFAULT_FREQUENCY_MINIMUM 1600

Thanks, Nick