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Difference b/w Digital I/O Control and Port Mapping Control

Ying Bai
Intellectual 295 points

There are two control strategies for GPIO ports in MSP432P401R MCU: General Digital I/O Control and Port Mapping Control.

In the former, alternate functions (Digital I/O function, primary module function, secondary module function, and third module function), can be selected by PxSEL1 & PxSEL0 registers with PxIN or PxOUT registers.

However, in the latter, the alternate functions are selected by mapping some pins to certain peripheral functions. But it looks like that both PxSEL1 & PxSEL0 are still needed.

What is the difference between these two methods?

Thanks,

  • 0
    Guru 23000 points
    Port Mapping, switches (MUX) connections between (some of) the Function Module and Output Module of each Port pin, and is located between both.
    The schematic principle of the function module can be found in the User’s Guide.
    The schematic principle of the output module can be found in the Data Sheet.
    The PxSELn bits are located inside the output module and selects the inner connections of this module. If the PxSELn connects the port-pin to his module i/o connection, this goes in fact to the port mapping switch which decides to which function module this will be connected.
  • 0 in reply to Leo Bosch
    Intellectual 295 points

    Leo,

    Thanks for your answer for my question.

    Yes, I think that is correct. However, between the Function module and GPIO modules, it should have Input and Output modules (not only Output module), such as UART RXD and SPI/SCI RX. Therefore, the Port Mapping Controller (or MUX) should be between Function Module and Input/Output modules of each pin.

    Thanks,

  • 0 in reply to Ying Bai
    Guru 23000 points

    You’re correct, I didn’t describe the Port-pin module correct. The ‘Output’ Module is an I/O Module and each pin have one. The I/O Module has inside for (most of) each Function Modules two Mapped connections, In (read) and Out (write).

  • 0 in reply to Leo Bosch
    Intellectual 295 points

    Thanks for your reply!

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