Initialization Information - STMicroelectronics SPC572L series Reference Manual

RM0400
The accumulator exception condition depends on whether or not it operates in saturated
mode as follows:
•
In Saturated operation (DECFILTER_MXCR bit SSAT=1): a sum exception occurs
(SSE=1) whenever an overflow is flagged; SSE asserts together with SSOVF.
• In Non-saturated operation (DECFILTER_MXCR bit SSAT=0): a sum exception occurs
(SSE=1) when an overflow is flagged and the DECFILTER_MXSR bit SSOVF is
already set to 1.
•
In Non-saturated operation, an accumulator exception also occurs if the accumulator
overflows twice without any update of the final integrator value DECFILTER_FINTVAL
or the current integrator counter DECFILTER_CINTCNT (by a read to the
DECFILTER_CINTVAL register), neither an integrator reset occurs. The SSOVF flag
does not assert in this situation.
Note: The SSOVF flag can only be asserted upon a hardware request, a software request, or
when DECFILTER_CINTVAL is read, based on the internal accumulator overflow state.
Similarly, the sample counter exception condition depends on whether or not it operates in
saturated mode as follows:
•
In Saturated operation (DECFILTER_MXCR bit SCSAT=1): a counter exception occurs
(SCE=1) whenever an overflow is flagged; SCE asserts together with SCOVF.
•
In Non-saturated operation (DECFILTER_MXCR bit SCSAT=0): a counter exception
occurs (SCE=1) when an overflow is flagged and the DECFILTER_MXSR bit SCOVF is
already set to 1.
•
In Non-saturated operation, a counter exception also occurs if the counter overflows
twice without any update of the final count DECFILTER_FINTCNT or the current
integrator counter DECFILTER_CINTCNT (by a read to the DECFILTER_CINTVAL
register), neither an integration reset occurs. The SCOVF flag does not assert in this
situation.
Note: The SCOVF flag can only be asserted upon a hardware request, a software request, or
when DECFILTER_CINTVAL is read (also updating DECFILTER_CINTCNT), based on the
internal counter overflow state.
37.5

Initialization Information

Following are some simple initialization steps to be performed before using the decimation
filter block. These steps assume that the user has already calculated the filter coefficients
using a filter design tool.
37.5.1 Initialization Procedure
The sequence of steps for the block initialization is as follows:
1. Program the configuration registers DECFILTER_MCR and DECFILTER_MXCR as
desired for your application.
2. Write all filter coefficient registers DECFILTER_COEFn with the previously calculated
values.
3. Enable the filter input, writing DECFILTER_MCR bit IDIS=0.
4. Run a soft-reset cycle if necessary.
5. The module is ready to receive data from the device slave-bus interface.
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Decimation Filter
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