SPRUJ17H March 2022 – October 2024 AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1
The [11-8] SAMPLE_DIV, [31-16] SAMPLE_CYCLES, [7-6] SCALE and [5-0] NOISE_BLOCKS bit fields in the TRNG_CONFIG 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 TRNG_CONFIG 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.