
Digital filter for sigma delta modulators (DFSDM)
RM0351
720/1830
DocID024597 Rev 5
24.4.10 Analog
watchdog
The analog watchdog purpose is to trigger an external signal (break or interrupt) when an
analog signal reaches or crosses given maximum and minimum threshold values. An
interrupt/event/break generation can then be invoked.
Each analog watchdog will supervise serial data receiver outputs (after the analog watchdog
filter on each channel) or data output register (current injected or regular conversion result)
according to AWFSEL bit setting (in DFSDM_FLTxCR1 register). The input channels to be
monitored or not by the analog watchdog x will be selected by AWDCH[7:0] in
DFSDM_FLTxCR2 register.
Analog watchdog conversions on input channels are independent from standard
conversions. In this case, the analog watchdog uses its own filters and signal processing on
each input channel independently from the main injected or regular conversions. Analog
watchdog conversions are performed in a continuous mode on the selected input channels
in order to watch channels also when main injected or regular conversions are paused
(RCIP = 0, JCIP = 0).
There are high and low threshold registers which are compared with given data values (set
by AWHT[23:0] bits in DFSDM_FLTxAWHTR register and by AWLT[23:0] bits in
DFSDM_FLTxAWLTR register).
Table 157. Integrator maximum output resolution (peak data values from integrator
output) for some IOSR values and FOSR = 256 and Sinc
3
filter type (largest data)
IOSR
Sinc
1
Sinc
2
FastSinc
Sinc
3
Sinc
4
Sinc
5
x
+/- FOSR. x +/- FOSR
2
. x +/- 2.FOSR
2
. x
+/- FOSR
3
. x
+/- FOSR
4
. x +/- FOSR
5
. x
4
-
-
-
+/- 67 108 864
-
-
32
-
-
-
+/- 536 870 912
-
-
128
-
-
-
+/- 2 147 483
648
-
-
256
-
-
-
+/- 2
32
-
-