Texas Instruments SimpleLink CC2620 Technical Reference Manual page 1172

Random Number Generator Registers
16.7.1.7 CFG0 Register (Offset = 18h) [reset = 0h]
CFG0 is shown in
Configuration 0
31 30 29 28
15 14 13 12
RESERVED
R-0h
Bit Field
31-16 MAX_REFILL_CYCLES
15-12 RESERVED
11-8 SMPL_DIV
7-0 MIN_REFILL_CYCLES
1172
Random Number Generator
Figure 16-10 and described in
Figure 16-10. CFG0 Register
27 26 25
MAX_REFILL_CYCLES
11 10 9
SMPL_DIV
R/W-0h
Table 16-12. CFG0 Register Field Descriptions
Type Reset
R/W 0h
R 0h
R/W 0h
R/W 0h
Copyright © 2015, Texas Instruments Incorporated
Table 16-12.
24 23 22 21
R/W-0h
8 7 6 5
MIN_REFILL_CYCLES
Description
This field determines the maximum number of samples (between 2
24
and 2 ) taken to re-generate entropy from the FROs after reading
out a 64 bits random number. If the written value of this field is zero,
the number of samples is 2
equals the written value times 2
24
0x0000: 2 samples
8
0x0001: 1*2 samples
8
0x0002: 2*2 samples
8
0x0003: 3*2 samples
...
8
0x8000: 32768*2 samples
8
0xC000: 49152*2 samples
...
8
0xFFFF: 65535*2 samples
This field can only be modified while CTL.TRNG_EN is 0.
Software must not rely on the value of a reserved. Writing any other
value than the reset value may result in undefined behavior.
This field directly controls the number of clock cycles between
samples taken from the FROs. Default value 0 indicates that
samples are taken every clock cycle,
maximum value 0xF takes one sample every 16 clock cycles.
This field must be set to a value such that the slowest FRO (even
under worst-case
conditions) has a cycle time less than twice the sample period.
This field can only be modified while CTL.TRNG_EN is '0'.
This field determines the minimum number of samples (between 2
14
and 2 ) taken to re-generate entropy from the FROs after reading
out a 64 bits random number. If the value of this field is zero, the
number of samples is fixed to the value determined by the
MAX_REFILL_CYCLES field, otherwise the minimum number of
samples equals the written value times 64 (which can be up to 2
To ensure same entropy in all generated random numbers the value
0 must be used. Then MAX_REFILL_CYCLES controls the minimum
refill interval. The number of samples defined here cannot be higher
than the number defined by the 'max_refill_cycles' field (i.e. that field
takes precedence). No random value will be created if min refill >
max refill.
This field can only be modified while CTL.TRNG_EN = 0.
0x00: Minimum samples = MAX_REFILL_CYCLES (all numbers
have same entropy)
6
0x01: 1*2 samples
6
0x02: 2*2 samples
...
6
0xFF: 255*2 samples
SWCU117C – February 2015 – Revised September 2015
www.ti.com
20 19 18 17
4 3 2 1
R/W-0h
24
, otherwise the number of samples
8
.
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16
0
8
6
14
).