• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 30 subscribers
  • Views 470 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TM4C123GH6PM: Unable to write to DR (data) register when using MICROWIRE SSI mode

Cameron Carslake
Prodigy 20 points
Part Number: TM4C123GH6PM

Hi All

I am having trouble with writing to the SSI data register.

The problem only occurs when using MICROWIRE mode, Freescale and TI modes work fine.

I have tried SSI 0..3 and same issues occurs.

When observing the memory of the data register, no changes can be seen however they can be seen using the other modes.

Is this a known issue with the Tiva C? 

  • 0
    TI__Guru**** 190406 points
    Hi,
    What off-chip device are you interfacing with? The MicroWire operates in a master-slave technique at half-duplex. If the master is sending something out on the MOSI pin you won't see slave transmitting on the MISO pin at the same time.
  • 0 in reply to Charles Tsai
    Prodigy 20 points
    Hi Charles

    The off chip device is an AD7918 analog to digital converter.
    But i have not interfaced to this device yet. I am using the internal loopback mode to check if the system on the Tiva is working first.

    Even though MICROWIRE is half-duplex, i should still see data written to the data register when observing the register and memory location, is this correct?

    I have observed this with the other two modes.
  • 0 in reply to Cameron Carslake
    TI__Guru**** 190406 points
    Hi,
    Are you saying that you don't see the SSIDR register value changed when you observe the register in the CCS register window? If this is the case, I think it is expected. When you read from the SSIDR the hardware actually read from the receive FIFO, not directly from the SSIDR register. So if you meant to see the value that you just wrote to the SSIDR and try to read back it will show 0 in the CCS register window. This behavior should be the same even for Freescale mode. I will suggest that you try in non-loopback mode and see if the data actually comes out on the MOSI signal for best evidence that it is working.

    This below post may be also helpful.
    e2e.ti.com/.../1620808