TCAN4550: State Diagram

HI AP,

I apologize for the confusion.  I've looked at this on an EVM and can observe that the INH pin is active and High when the device is in the UVIO protected state which is consistent with the state diagram and the text description.  However, this protected state only exists for 200-500ms and if VIO has not recovered to value greater than the UVIO threshold, then the device will transition to Sleep Mode and INH will be disabled in Sleep Mode.

I will also note that the PWRON bit must be cleared in order for the 200-500ms UVio Timer to run and cause the device to transition from the UVio Protected State to Sleep Mode.  If the PWRON bit has not been cleared following the initial Power On or Reset event, then the INH pin will remain High while the VIO voltage is low.  This is to prevent unwanted power cycle oscillations if the INH pin is controlling the low voltage regulator sourcing VIO and the MCU during the initial startup.  Once the system is active, the VIO supply should be stable and the MCU can clear the PWRON bit allowing the UVio Timer to run during a UVio condition. 

AP said:

Which is correct? Is the INH state a safe HW indicator for "TCAN4550 is definately in Sleep mode of all the modes"?

The INH pin will be Hi-Z when the device is in Sleep Mode, and it will be High when the device is in any other mode.

AP said:

And another question for the State Diagram:
States Standby Mode, TSD Protected and UVIO Protected show "Wake Sources: WAKE" or "CAN, WAKE" inside the state block. I can see the wake event effect when in Sleep mode. But what is the effect of a wake event (bus or pin) in the other states mentioned above?

The only other mode in the diagram is Normal mode which does not have any WAKE sources because the device is already operating in Normal Mode. 

Regards,

Jonathan

Hi Jonathan,

INH is clear now, thanks for looking this up.

But for the other question again (wake sources shown in state diagram blocks, not arrows): Standby Mode, TSD Protected Mode and UVIO Protected Mode have written in their "blocks": "Wake Sources: CAN Bus or WAKE Pin". But there are no arrows shown that a wake event would leave any of these states. So I'm wondering about the "Wake Sources" statement in the state blocks of these states. 

E.g. why is it good to know, that e.g. in TDS Protected Mode their is an active "Wake Source"?  Does a wake event immediately leave the TSD state (though there is no arrow indication for this), and if so to which state? Or what is the effect of a wake event in TSD state (as an example, same question for Standby Mode state). Sleep Mode state clearly shows that a wake event will move state to Standby (wake event arrow). But Standby and TSD states only have the text inside the block, no "wake event" arrows, and I don't really know what to make of it.

Thanks

Added:

I just noticed the small note on the left of the state diagram (blind to it before): I guess that means that a wake event in any state with an active wake source will leave the current state and move to Standby Mode state (even if such an "arrow" is not shown in the diagram)?

Added:

I have come to this "conclusion":

The small note on the left of the state diagram "belongs" to the Sleep Mode state only (a note for transitions from Sleep to Standby).

The other states (other than Normal or Sleep) with an active "wake source" would still indicate a wake event by nWKRQ and/or interrupt, but will not change the state (just because of the wake event). Is this more or less correct?

Hi AP,

The UVio Protected and TSD Protected states are by definition "protected" because either the voltage level is too low to properly operate, or the temperature is too high for the device to function normally.  The only way to exit one of these "protected" states is for the voltage or temperature level to return to normal and safe levels so that the device will function as expected.  

The digital core is not disabled while the device is in one of these protected states, so a WAKE event may be detected.  However, the device will remain in the protected state as long as the voltage or temperature condition is outside the proper operating range.  Once that condition has cleared, the wake signal can be detected.

So to be clear, the UVio Protected state will be entered and exited only based on the VIO voltage level.  Likewise the TSD (Thermal Shutdown) Protected state will be entered and exited only based on the internal die temperature.

The events indicated by the arrows in the diagram will cause a state change.  The device will only transition to Standby Mode from a Wake Event when the device is in Sleep Mode.  

Regards,

Jonathan