Arm True Random Number Generator (TRNG) configuration parameters specify the settings of the internal ring-oscillator lengths, and the output sampling rate. The parameters are device-specific.
Each silicon process has different noise and jitter characteristics. The specific SoC layout affects these characteristics. Therefore, the TRNG behavior must be characterized on the actual silicon of the device to determine the most suitable parameters. Characterizing in this way ensures that the TRNG output has maximal entropy.
Characterization must be performed during the initial post-silicon testing of the device, or whenever substantial changes are made. For example, after changes to process or respins.