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TM4C1294NCPDT: SSI module questions

Priya Nadathur70
Expert 2795 points

Part Number: TM4C1294NCPDT

Looking at the TivaC datasheet, there is clarity about half duplex and full duplex set up of the SSI module.

Is the SSI module in the  LM3S5B91 half duplex only?

Can an SSI module interface with any SPI module just by hooking up the 4 signals if the same frame

format is used?

Thanks,

Priya

  • 0
    TI__Guru*** 135355 points
    Hello Priya,

    The SSI module of the LM3S device can be both full or half duplex. All common applications for it used full duplex mode.

    Not sure what you mean by frame format, but an important consideration when hooking up any SPI peripheral to an MCU is to make sure the MCU and peripheral have the same clock polarity and clock phase settings. Also you need to look at min/max clock speeds as well.
  • 0 in reply to Ralph Jacobi
    Guru 117855 points

    *** LIKE *** ..... especially, "All common Apps use "full duplex mode."

    As "full duplex" arrives "free" - unless simplicity is the major goal - it should be the "mode of choice."     (complexity results especially when SPI manages a "Command-Response" design ... (i.e. those in which the Slave device - presently receiving a "new command" - is (simultaneously) sending "response data" - which is in satisfaction of a (previous/earlier) issued, Master Command.    Thus the Slave's response is always (one or more) SPI transactions "behind."    (more resulting when the quantity of data sent by the Slave exceeds a "single SPI Frame's" data capacity)

    Thinking about "Full/Half duplex" bit further - as the Master device provides the SPI clock - even when - and especially when - the Master is providing "don't care/dummy" output data - that output is "still" on the wire - thus "real/conventional" Half-Duplex may not "really/officially" be possible.   (especially when compared/contrasted to other "serial communications" (i.e. UART) in which "real, one way, non-simultaneous" transactions - often occur...)

    As to "frame format" - that term (was) used by earlier (LM3S/LX4F) manuals (also by other vendors) - and to my mind - specifies: clock polarity, phase, and (sometimes) data length while output signal "CS" persists and/or remains active...