SPRUJB6B November 2024 – May 2025 AM2612
The [11-8] SAMPLE_DIV, [31-16] SAMPLE_CYCLES, [7-6] SCALE and [5-0] NOISE_BLOCKS bit fields in the register determine the number of clocks needed to generate the first random value.
The run time for a single output block is always the same: SAMPLE_CYCLES * (4SCALE) * NOISE_BLOCKS * 512 * trng_clock_period * (SAMPLE_DIV + 1). The BC_DF function is continuous and must be run long enough to generate 384 bits and according to the NOISE_BLOCKS description, that requires a setting of 12 in there.
When generating raw noise bits for processing by the BC_DF function, the bit rate as controlled by the [11-8] SAMPLE_DIV, [31-16] SAMPLE_CYCLES, and [7-6] SCALE bit fields in the register may not be set higher than one bit per three module clocks.
When sufficient entropy is generated to seed the DRBG, the FROs are switched-off to conserve power. When a reseed is done, the FROs are enabled again. This process takes the same amount of time as a cold start of the TRNG.