SPRUIZ1B July 2023 – August 2024 TMS320F28P650DH , TMS320F28P650DK , TMS320F28P650SH , TMS320F28P650SK , TMS320F28P659DH-Q1 , TMS320F28P659DK-Q1 , TMS320F28P659SH-Q1
The mismatch test mode creates an error output of 1 on each individual comparator (bit) within the comparator block, one at a time. This makes sure that all comparators in the block are working correctly and that a fault is successfully propagated to the module output.
This test is executed using a walking 1s pattern to test for output-stuck-at-zero issues. The walking 1s pattern is where all comparators in the comparator block are zero except for one of the comparators.
For example, the primary module has a 1 at the spot that the secondary module has a 0. This can force an intentional error.
This is repeated for every comparator in the block, with the 1 being set on both modules. The passing scenario for this is that all comparators see a mismatch, flagging a mismatch each iteration. See Figure 38-2 for a simplified illustration of how this is implemented for a comparator block with 8 comparators (not the number used in the actual design).