Partial Rng Shutdown: Input Clock Cut Off - Texas Instruments OMAP5912 Reference Manual

Figure 22. Total Automatic RNG Shutdown
Clock and
reset module
OCP clock
Clock
reference
cutted (4)
External
clocks
ULPD
ARM926EJS

Partial RNG Shutdown: Input Clock Cut Off

SPRU753A
Input system clock
(OCP)
cutted (5)
RNG idle signal
No read (1)
indication (3)
The second safest wayto reduce RNG module consumption is to cut the input
clock (OCP). The state machine does not jump any more to the different states,
the entropy is preserved in the system, and cutting the clock does not affect
the randomness. The input clock can be restarted anytime and no reset is
needed to correctly restart the RNG module.
Because the state machine can be in any state when the input clock is cut off,
one of the rings can still be on. The state machine does not reach the
IDLERNG anymore, so the ring is still on. Hence, there is a penalty on power
consumption reduction.
Power Management User Services
RINGS
oscillators
disable (2)
Output
registers
Input
registers
Power Management
RNG
generator
State
machine
RNG module
OMAP 5912
81