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RTOS/TM4C129XNCZAD: External SRAM and EMAC EPI limitation

Adnan Ahmad
Prodigy 20 points

Part Number: TM4C129XNCZAD

Tool/software: TI-RTOS

Hi,

Below are few links on TI forum discussions which suggests that we cannot use EMAC functionality if we use External RAM for it. 

https://e2e.ti.com/support/microcontrollers/tiva_arm/f/908/p/497367/1812046

https://e2e.ti.com/support/microcontrollers/tiva_arm/f/908/p/418477/1503808

https://e2e.ti.com/support/microcontrollers/tiva_arm/f/908/t/517238

The pointers used by EMAC must refer to a buffer in internal SRAM.  Pointers to flash or EPI-connected memory may not be used and will result in the MAC reporting a bus error. Please see the comments in Src\Driverlib\emac.h file as well.

I just wanted to understand if this is correct understanding that 'all' Ethernet HTTP client and Webserver related code need to use internal RAM and cannot use external SRAM or SDRAM?

Thanks

 

  • 0
    Guru 117855 points

    While firm/I cannot assist w/the specifics of "129x" - your post deserves "memorialization" due to its: "Clarity, supporting links, detail, and high focus."

    Your post well demonstrates great care, thought & effort - and that (continued) practice - is an excellent predictor of your future success.

    Very nice job!     Your key effort should best enable vendor staff to respond quickly & efficiently.

  • 0
    TI__Guru 72500 points

    At the least, the buffers must be copied to the internal SRAM before they can be used by the EMAC. (Short note buried on page 1599 of the datasheet.)