PMM Operation
206
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Power Management Module (PMM)
3.3.8.2
Self-Test Mode
A self-test mechanism is provided to check the PSCON compare logic for faults. The compare error signal
output is disabled in self-test mode. The PSCON diagnostic compare block generates two types of
patterns during self-test mode: compare match test followed by compare mismatch test. During the self-
test, each test pattern is applied on both PSCON signal ports of the PSCON diagnostic compare block
and then is clocked for one cycle. The duration of the self-test is 24 cycles. Any detected fault is indicated
as a self-test error, mapped to ESM group1 channel 39. If no fault is detected, the self-test complete flag
is set.
The application can poll for this flag to be set and then switch the mode of the PSCON compare block
back to lock-step mode by writing to the mode key register.
NOTE:
PSCON operation when compare block is in self-test mode
When the PSCON compare block is in its self-test mode, both PSCONs continue to function
normally. However, there is no comparison done on the PSCON outputs.
Compare match test:
An identical vector is applied to both input ports at the same time, thereby expecting a compare match. If
the compare unit produces a mismatch then the self-test error flag is set and the self-test error signal is
generated. The compare match test is terminated if a compare mismatch is detected. The compare match
test takes 4 cycles to complete when the test passes.
Compare mismatch test:
A vector with all 1's is applied to the PSCON diagnostic compare block’s primary input port and the same
input is also applied to the secondary input port but with one bit flipped starting from bit position 0. The
unequal vectors should cause the PSCON diagnostic compare block to generate a compare mismatch at
bit position 0. In case a mismatch is not detected, a self-test error is indicated. This compare mismatch
test algorithm is repeated until every single bit position is verified on both PSCON signal ports.
3.3.8.3
Error-Forcing Mode
This mode is designed specifically to ensure that the error signal output from the PSCON compare block
is not stuck inactive. In this mode, a test pattern is applied to the PSCON related inputs of the compare
logic to force an error. During error forcing mode, both the error signal and the self-test error signal will be
asserted to the ESM. The application can clear flags for ESM group1 channel 38 and ESM group1
channel 39 once the error is flagged. If the two ESM flags do not get set, this indicates that the PSCON
compare error signal is stuck inactive and cannot be relied upon to detect a PSCON mismatch.
3.3.8.4
Self-Test Error-Forcing Mode
In this mode, an error is forced so that the self-test error output from the PSCON compare block is
activated. The application can clear the flag for ESM group1 channel 39 once the error is flagged. If the
ESM group1 channel 39 flag does not get set, this indicates that the PSCON compare block self-test error
signal is stuck inactive and there is no self-test mechanism available for the PSCON compare block.
3.3.8.5
PMM Operation During CPU Halt Debug Mode
No compare errors are generated when the CPU is halted in debug mode, regardless of the mode of the
diagnostic compare block. No status flags are updated in this mode. Normal operation of the compare
block is resumed once the CPU exits the debug mode.