RM46L852 Error Pin Software Trigger

Hello Jarno,

Jarno Puff said:

I know the Error Pin of the TMS/RM series are triggered by the internal lockstep architecture. However, is there a way to use the same pin to signal a software code error?

I'm designing a Dual Modular Redundant flight controller as active/passive architecture using the RM46L852 and the TPS65381. The Error pin should trigger the TPS65381 and use its DRVENABLE pin to toggle a arbiter logic. But this should happen even as a lockstep HW error and as a software error (manually triggered, e.g. IMU sensor inconsistency values).

Any suggestions?

To be clear, the error pin is an active low pin that is driven low upon a group 2 (dedicated) or group 1 (configurablle) error.  There are several group 2 errors including the CCM error type as well as uncorrectable ECC error types. Group 1 includes some potentially less critical errors such as peripheral RAM parity errors, ECC correctable errors, IOMM configuration errors, etc. 

In regard to utilizing the nERROR pin within your application, it is possible to force an error condition using the ESM Error Key Rigister (ESMEKR) which will assert the nERROR pin for a defined amount of time. See section 12.2.3 in the TRM for more information.

Jarno Puff said:

Can I also share the MCU Error pin with other logics?

I am not 100% certain what you mean by this. Certainly it is up to you how you use the error pin and share it within your application. The key is to insure the appropriate action is taken upon identification of the errors within the MCU and activation of the nERROR pin. The specifics of the pin and it's loading capability is located in the device datasheet.

Jarno Puff said:

How can I drive a Error-LED using the Error Pin?

This would be no different than driving an LED with any other active low pin. For an example, please have a loop at the HDK or Launchpad schematics. the HDK schematic and related design files are located here: 

Jarno Puff said:

Is there also a way to reset external the TPS65381 to force a complete power cycle?

I think it would be best to ask the team from the PMIC group about this since they are the TPS65381 experts. Their forum is located here: 

Hi Chuck,

So I can manually trigger the nERROR pin within my application using the ESM Error Key Rigister (ESMEKR) which will assert the nERROR pin for a defined amount of time. If the nERROR pin is connected to the TPS65381, this will force a reset of the MCU. Is this correct?

The question about "sharing" the nERROR pin was related to share it with the TPS65381 and another logic pin (MCU or AND Gate).

Whether or not the TPS65381 does a reset is dependent on how you have hooked up the TPS device to the hercules device and how you have configured the nERROR pin handling by the TPS device. For certain, there is the possibility to connect the TPS so that it triggers a reset of Hercules based on reaction to nERROR but I believe the quantity of nERROR assertions that trigger a reset is programmable (via SPI interface).

As far as sharing is concerned, this should be OK as long as the the number of devices on the pin don't exceed the loading spec for the IO pin.