Analog-to-digital converter (ADC) RM0453
558/1454 RM0453 Rev 2
18.7.2 Description of analog watchdog 2 and 3
The second and third analog watchdogs are more flexible and can guard several selected
channels by programming the AWDxCHy in ADC_AWDxCR (x = 2, 3).
The corresponding watchdog is enabled when any AWDxCHy bit (x = 2,3) is set in
ADC_AWDxCR register.
When converting data with a resolution of less than 12 bits (configured through DRES[1:0]
bits), the LSB of the programmed thresholds must be kept cleared because the internal
comparison is always performed on the full 12-bit raw converted data (left aligned).
Table 106 describes how the comparison is performed for all the possible resolutions.
The AWD2/3 analog watchdog status bit is set if the analog voltage converted by the ADC is
below a low threshold or above a high threshold. These thresholds are programmed in
HTx[11:0] and LTx[11:0] of ADC_AWDxTR registers (x = 2 or 3). An interrupt can be
enabled by setting the AWDxIE bit in the ADC_IER register.
The AWD2 and ADW3 flags are cleared by software by programming them to 1.
18.7.3 ADC_AWDx_OUT output signal generation
Each analog watchdog is associated to an internal hardware signal, ADC_AWDx_OUT (x
being the watchdog number) that is directly connected to the ETR input (external trigger) of
some on-chip timers (refer to the timers section for details on how to select the
ADC_AWDx_OUT signal as ETR).
ADC_AWDx_OUT is activated when the associated analog watchdog is enabled:
• ADC_AWDx_OUT is set when a guarded conversion is outside the programmed
thresholds.
• ADC_AWDx_OUT is reset after the end of the next guarded conversion which is inside
the programmed thresholds. It remains at 1 if the next guarded conversions are still
outside the programmed thresholds.
• ADC_AWDx_OUT is also reset when disabling the ADC (when setting ADDIS to 1).
Note that stopping conversions (ADSTP set to 1), might clear the ADC_AWDx_OUT
state.
• ADC_AWDx_OUT state does not change when the ADC converts the none-guarded
channel (see Figure 79)
AWDx flag is set by hardware and reset by software: AWDx flag has no influence on the
generation of ADC_AWDx_OUT (as an example, ADC_AWDx_OUT can toggle while AWDx
flag remains at 1 if the software has not cleared the flag).
The ADC_AWDx_OUT signal is generated by the ADC_CLK domain. This signal can be
generated even the APB clock is stopped.
Table 107. Analog watchdog 1 channel selection
Channels guarded by the analog watchdog AWD1SGL bit AWD1EN bit
None x 0
All channels 0 1
Single
(1)
channel
1. Selected by the AWD1CH[4:0] bits
11
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