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RM46L852: SPI Port with RTC

Jeremiah Trest
Prodigy 20 points
Part Number: RM46L852

Hi, I am currently facing an issue while interfacing through SPI from a TI RM46 Hercules lockstep processor to the M41t94 RTC. The issue is that no matter what data or settings I send to the RTC, through an oscilloscope it just shows the in/output to be high. I have tried many different combinations of settings and nothing seems to work. I am thinking that there is some type of mode that I have to get out of, but I am not quite sure. Thank you!

  • 0
    TI__Guru**** 196426 points

    Hello,

    Which SPI is used to communicate with RTC? The SPI signals may multiplexed with other signals. For example, pin 25 (144PGE package) is used for N2HET1[0]/SPI4CLK/EPWM2B, and this pin is used as N2HET1[0] by default. If you want to use this pin as SPI4CLK, the pinmux for this pin should be configured properly:1.

    1. enable SPI4 module:

    2. Configure the pinmux

    The pins are automatically selected for SPI4

    3. Configure SPI4, then generate code

  • 0 in reply to QJ Wang
    Prodigy 20 points

    Hi QJ,

    Thanks for the help, but this was not the issue. We are actually currently using SPI2 to interact with the RTC, and it does not seem that any of the lines that are being used to communicate with the RTC are being multiplexed. We are using SPI2CLK, SPI2CS0, SPI2SIMO,and SPI2SOMI. The curious thing is that no matter if we assign any of these ports to GPIO and set them to low, they still read high on an oscilloscope. This jumps out to me as a hardware issue, but I am not sure if you would know anything about this architecture that would make this happen through software. 

    Thank you

  • 0 in reply to Jeremiah Trest
    TI__Guru**** 196426 points

    Hello,

    RM46Lx device supports two packages: 337-ball ZWT (BGA) package and 144-pin PGE package. The ZWT package has SPI2, but PGE package doesn't have SPI2 module. Which package are you using? Do you use TI launchpad or your won hardware board?

    If using your own PCB board, please double check that the SPI2 signals are routed out from ball E2/N3/D1/D2.