MC33774A – Questions Regarding ALARM_OUT Pin Configuration

[varunbharti]

Hello NXP Community,

I’m currently working with the MC33774A AFE and have several questions related to the ALARM_OUT pin configuration. I would appreciate your guidance on the following points:

1. Toggle Functionality: How can I configure the ALARM_OUT pin to toggle whenever any of the configured alarms are triggered?

2. Enablement: Is there a specific bit or register setting required to activate or enable the ALARM_OUT functionality?

3. Heartbeat Mode Issues: While testing the ALARM_OUT pin in heartbeat mode, I’ve observed inconsistent behavior—sometimes it works, other times it fails. Has anyone experienced similar issues, or have suggestions for a reliable configuration?

4. Reconfiguration: Can the ALARM_OUT pin be reconfigured dynamically during runtime, or should it be set only once during initialization?

5. UV Detection Use Case: I aim to use the ALARM_OUT pin for undervoltage (UV) detection, where the pin should go high when UV is detected. How can I reuse the same pin to detect UV events repeatedly without needing to reconfigure the entire analog front end (AFE)?

6. Multiple Alarm Events: Is it possible to configure the ALARM_OUT pin to respond to multiple alarm conditions multiple times—i.e., without resetting the MCU or the AFE after each event?

Any insights, register materials, or sample configuration steps would be extremely helpful.

Thank you in advance!

[ErikaC · Accepted solution]

1. Toggle Functionality: How can I configure the ALARM_OUT pin to toggle whenever any of the configured alarms are triggered?configure FEH_ALARM_CFG (configuration of ALARMOUT signal),  FEH_ALARM_OUT_CFGx (event(s) that will activate ALARMOUT),  and the thresholds (for instance PRMM_AIN0_OV_TH_CFG for an overvoltage detection on AIN0). All configuration information are described in the datasheet.The measurements should be of course enabled (periodic).
   
   

2. Enablement: Is there a specific bit or register setting required to activate or enable the ALARM_OUT functionality?See answer above; when a fault occurs, to clear the ALARMOUT signal, it is required to read both registers FEH_ALARM_OUT_REASON0 and FEH_ALARM_OUT_REASON1

3. Heartbeat Mode Issues: While testing the ALARM_OUT pin in heartbeat mode, I’ve observed inconsistent behavior—sometimes it works, other times it fails. Has anyone experienced similar issues, or have suggestions for a reliable configuration?what means inconsistent behavior ? when the ALARMOUT hearbeat is activated and no fault occuring then the ALARMOUT toggles permanently at the expected period. No issue reported

4. Reconfiguration: Can the ALARM_OUT pin be reconfigured dynamically during runtime, or should it be set only once during initialization?yes

5. UV Detection Use Case: I aim to use the ALARM_OUT pin for undervoltage (UV) detection, where the pin should go high when UV is detected. How can I reuse the same pin to detect UV events repeatedly without needing to reconfigure the entire analog front end (AFE)? you have to clear the ALARMOUT fault reason. You can change the source selection if needed by configuring FEH_ALARM_OUT_CFG0 and CFG1. Don't need to reconfigure the entire analog frontend

6. Multiple Alarm Events: Is it possible to configure the ALARM_OUT pin to respond to multiple alarm conditions multiple times—i.e., without resetting the MCU or the AFE after each event? yes, see answers above

[varunbharti]

Thankyou

[RafaR]

Please refer to: MC33774A : Question Regarding Alarm and Wakeup Pin Configuration

Have a great day and best of luck.