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TMS320DM816x DaVinci Unused Pins

Phillip Dingman
Prodigy 40 points
Other Parts Discussed in Thread: TMS320DM8168

In sprugx8 reference sheet it states in section 3.2.6.5  "refer to data manual sections on Pin Mulitplexing Control and how to handle unused pins."

I could not find this.

Your TI tool was used for assigning Pinctrl, but found some errors in it.

Question:  For unused pins, how should the Pinctrl be set?     Is it reasonable to set the pin mode to an undefined functional mode with a pull down?  I see this as a default in some of the cases.

The tool is not consistant on how it deals with unused pins.

 

 

 

  • 0
    Intellectual 490 points

    Hi Phillip,

    I recall reading about what do with unused pins the other day, and found it in Section 4.6 in this document:

    http://www.ti.com/lit/ds/symlink/tms320dm8168.pdf

    When device signal pins are unused in the system, they can be left unconnected unless otherwise instructed in the Terminal Functions tables. For unused input pins, the internal pull resistor should be enabled, or an external pull resistor should be used, to prevent floating inputs. All supply pins must always be connected to the correct voltage, even when their associated signal pins are unused, as instructed in the Terminal Functions tables in Section 3.2.

    Section 4.3.1 has some guidelines on pull-up/pull-down resistors.

    However, I'm not sure about what mode to set the unused pins to.  In section 4.5 it states that the default pinctrl mode is 0x000, I would assume that for unused pins it is ok to leave it at that, but hopefully someone else can confirm.

    Aaron

  • 0 in reply to Aaron Ridinger
    TI__Guru**** 393215 points
    Hi Philip, Aaron,
     
    This is correct, DM816X Datasheet section 4.6 is the source of information for unused pins, along with tables in section 3.2. As for muxmode, it's not relevant for unused pins. If possible, it would be best to configure unused pins as inputs with pulldown resistor enabled.
     
  • 0 in reply to Biser Gatchev-XID
    TI__Genius 10190 points

    Each pin has 4-Mux modes (M0, M1, M2, M3).  However most or all do not have an entry for each mode.  E.g. M0 – Nothing in table, M1 – GPOx, m2-EMAC1_dx, M3 – Nothing in table.

    Question:

    For the example Pin above, assume it is not used in our design.   I’d like to set to M3 mode with a pull down.

    Is this valid?

    Thought is I do not want to take a chance that something is accessing M1 or M2 function in the Off the shelf software or perhaps that functionality was assigned to another pin.

    What does the hardware do when I select a Mux Mode, M3 for example, that does not have functionality assigned to it?

    It’s not clear or perhaps I’m not reading the specification correctly… I’ve been looking at the Tech spec and have not looked at the datasheet in detail yet.

  • 0 in reply to Mark Ackerson
    TI__Guru**** 393215 points
    Hi Mark,
     
    The DM816X TRM section 4.5:
     
    "Device-level pin multiplexing is controlled on a pin-by-pin basis by the MUXMODE bits of the PINCTRL1 - PINCTRL321 registers in the SYSCFG module. The default state for each multiplexed pin is MUXMODE = 0x000.
     
    Pin multiplexing selects which of several peripheral pin functions control the pin's IO buffer output data values.
     
    The input from each pin is routed to all of the peripherals that share the pin, regardless of the MUXMODE setting."
     
    Based on the above I think that all muxmode values are valid. Muxmode is irrelevant if you set the pin as an input.