Revisions Affected

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Details

The CMPSS latched path is designed to retain a tripped state within a local latch (COMPxLATCH) until it is cleared by software (via COMPSTSCLR) or by PWMSYNC.

COMPxLATCH is set indirectly by the comparator output after the signal has been digitized and qualified by the Digital Filter. The maximum latency expected for the comparator output to reach COMPxLATCH may be expressed in CMPSS module clock cycles as:

When COMPxLATCH is cleared by software or by PWMSYNC, the latch itself is cleared as desired, but the data path prior to COMPxLATCH may not reflect the comparator output value for an additional LATENCY number of module clock cycles. If the Digital Filter output resolves to a logical 1 when COMPxLATCH is cleared, the latch will be set again on the following clock cycle.

Workarounds

Allow the Digital Filter output to resolve to logical 0 before clearing COMPxLATCH.

If COMPxLATCH is cleared by software, the output state of the Digital Filter can be confirmed through the COMPSTS register prior to clearing the latch. For instances where a large LATENCY value produces intolerable delays, the filter FIFO may be flushed by reinitializing the Digital Filter (via CTRIPxFILCTL).

If COMPxLATCH is cleared by PWMSYNC, the user application should be designed such that the comparator trip condition is cleared at least LATENCY cycles before PWMSYNC is generated.