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F28377S and Tiva MCU sharing RAM

Hello.

We are advancing in our designs and now we have reached the point where more processor muscle is needed (always  power-aware), so we have decided to introduce a C2000 DSP MCU (F28377S - D) within our Tiva board.

The communication between devices is going to be via SPI, however, it is interesting to us to introduce some external RAM (probably SDRAM) connected via EMIF to the DSP. We think it would be very interesting, if both CPUs could share that external RAM so many blocks of data could be readable from both CPUs at high speed. In our design the DSP would be the Master and Tiva the slave....of course some SW priorities should be introduced.

However, we are aware that Tiva devices only have an EPI peripheral for external memories.

Is it possible for te DSP and Tiva  share that RAM? In the Tiva forum, some person recommended maybe a Dual port SDRAM, is it possible?

Is there any other "similar" solution? Some MBs of RAM should be enough for us.

Thank you.

  • Hi,

    F28377S device has EMIF IP which can interface to external SDRAM memories but as suggested by someone from TIVA device team, you need to have dual port SDRAM memory to share the same memory with other controller.

    Regards,

    Vivek Singh

  • Vivek Singh said:

    F28377S device has EMIF IP which can interface to external SDRAM memories but as suggested by someone from TIVA device team, you need to have dual port SDRAM memory to share the same memory with other controller.

    Regards,

    Vivek Singh

    Thank you Vivek.

    Is there an example of an schematic for the EMIF IP port and a SDRAM? I have checked the forum but I haven't found anything.

    Would you recommend a specific Dual port RAM IC?

    Thank you.

  • Hello Vivek, could you give me a hand with this?
    Thank you
  • I see that Cypress has several available dual port RAM ICs. That might be a good starting point. If I were you, I would try to procure a sample, or an eval board, or make your own eval board by mounting it onto a "Schmartboard." Then connect to both processors, maybe one at a time. Make sure they can access the RAM independently, then together. Sounds like a lot of work? Yes, it could be, depending on the interfaces of each of the processors.
  • Thank you Todd. I will look into it.

    Do you know any example of an schematic for the F28377X family with SDRAM? I haven't found anything yet.

    Regards

  • Take a look at
    processors.wiki.ti.com/.../C2000_Archived_Workshops

    and go to 3.4.3 C2000 Delfino Multi-Day workshop. If you look at the Student Guide under System Design, you will see several pages dedicated to the external memory interface. Bear in mind this is the F28335, so there may be some differences between that and the F28377x, but it is at least a starting point...
  • Hi,

    Few points to note -

    Cypress RAMs are SRAM and not SDRAM. We have not used dual-ported SDRAM and I can not find one online. If it's not available then you have to use dual ported SRAM/ASRAM only.

    External interface (XINTF) module on F28335 does not support SDRAM interface but external interface (EMIF) module on F28377S device supports SDRAM as well but we don't have recommended schematic. These are standard memory interface and all the signals are mapped 1 to 1 from controller to external memory except address pins which need some precaution based on what type (16/32 bit) memory is used (for SRAM/ASRAM interface). Please refer section "25.3.6.1 Interfacing to Asynchronous Memory" of TRM for more detail on this.

    Regards,

    Vivek Singh

       

  • Thank you Vivek.

    Do you have at least an example of schmetic or pinout connection with a single SDRAM and a F2837xx device?

    It would be very helpful, since we have to develop a new board with no reference at all.

    Regards

  • Hello Vivek.
    Even a SRAM schematic example would be great for us. Could you provide one?

    Thank you.
  • Take a look at ezDSP schematics

    ezDsp_28335_schematics.pdf

  • Hi,
    I hope you were able to get the required info. Let us know if you have any addition query.

    Vivek Singh
  • Thank you Vivek for your interest. We are still designing the board.

    We still haven't found any simple SDRAM connection example, but one with SRAM.

    Would you be able to provide one?
    Is there any significal advantge of one above the other besides speed?

    Regards.
    PAk
  • Sorry, we do not have board schematic for this use case. On this device there is not much difference between SDRAM and SRAM performance so you can use the SRAM itself.

    Regards,

    Vivek Singh
  • Vivek Singh said:
    Sorry, we do not have board schematic for this use case. On this device there is not much difference between SDRAM and SRAM performance so you can use the SRAM itself.

    Regards,

    Vivek Singh

    Thank you.

    Could you recommend any commercial SRAM device bigger than 64Mb and link  a valid schematich to work with?

    Thank you again

  •  

    PAk said:

    Could you recommend any commercial SRAM device bigger than 64Mb and link  a valid schematich to work with?

    Thank you again

    ?

    For this commercial SRAM device  at least 64Mb, is it possible to be 32bit wide or would it be eaxsier to work with a 16bit wide one?

    Could you recommend any examples of devices?

    Thank you again

  • Hi,

    Sorry for late reply.

    If you are using ASRAM (not SDRAM) then this device does not support 64Mb address space for the same.

    Regards,

    Vivek Singh

  • Vivek Singh said:
    Hi,

    Sorry for late reply.

    If you are using ASRAM (not SDRAM) then this device does not support 64Mb address space for the same.

    Regards,

    Vivek Singh

    Then, which are the options for sram?

  • Hello again.
    Could you please answer my question?

    Thank you
  • Hi,

    We are still not clear which external memory device you are planning to use. Please clarify the same.

    Regards,

    Vivek Singh

  • Depending on the max size of the memory itself we could go asram or sdram.

    Anyway a small guidance would be helpful
    Regards
  • Available address space for SDRAM is bigger compare to ASRAM.

    Please check MT48LC32M16A2 from Micron technologies.  This is just for reference. Customer should use device which works best fro them.

    Regards,

    Vivek Singh

  • Vivek Singh said:

    Available address space for SDRAM is bigger compare to ASRAM.

    Please check MT48LC32M16A2 from Micron technologies.  This is just for reference. Customer should use device which works best fro them.

    Regards,

    Vivek Singh

    Thank you Vivek.

    Finally we decided to go SDRAM due to size. We have seen TI tested their examples with MT48LC32M16A2P-75 IT:C, could you provide a simple scheme to route of on board?

    Regards

  • Hello Vivek.
    Would you have any information about this issue that could help us?

    regards
  • Hi, We do not have reference design for this to share with customer since this is standard interface. I could provide you xls sheet with pin mapping for SDRAM interface. Let me know if that would work.

    Regards,
    Vivek Singh
  • Thank you Vivek.
    That would work great. We just need some "assurance" with our first design with C2000.

    Regards
  • Hi, Hope attached image provides you required info. Please note this is only for reference. User need to make sure all the connections are as per datasheet.

    Let us know if you have any addition queries.

    Regards,

    Vivek Singh

  • Thank you Vivek.

    Checking this pinout map against the PinMux utility, setting it for SDRAM 16bit, I have seen that mostly everything is there but I have seen some discrepancies.

    For example, the pins EM1A13, EM1A14, EM1A19 and EM1A20 are not routed as EM1CAS,EM1RAS, EM1BA1 and EM1BA2 respectively. (However they seem to be the same GPIOXX pin).

    On the other hand, pins EM1A14 and EM1A15, ar not routed by pinmux. Probably they should be EM1DQM0 and EM1DQM1....

    My (reasonable) doubts are:

    • Is this a bug on the application?
    • Why two names for the same pins?

  • Hi,

      For example, the pins EM1A13, EM1A14, EM1A19 and EM1A20 are not routed as EM1CAS,EM1RAS, EM1BA1 and EM1BA2 respectively. (However they seem to be the same GPIOXX pin).

    I see these pins are included in SDRAM configuration. Which version of tool you are using?

    On the other hand, pins EM1A14 and EM1A15, ar not routed by pinmux. Probably they should be EM1DQM0 and EM1DQM1....

    C28x does not support byte access (only 16bit/32bit access) so these signals are optional.

    Regards,

    Vivek Singh

  • Vivek Singh said:

    Hi,

      For example, the pins EM1A13, EM1A14, EM1A19 and EM1A20 are routed as EM1CAS,EM1RAS, EM1BA1 and EM1BA2 respectively. (However they seem to be the same GPIOXX pin).

    I see these pins are included in SDRAM configuration. Which version of tool you are using?

    On the other hand, pins EM1A14 and EM1A15, are not routed by pinmux. Probably they should be EM1DQM0 and EM1DQM1....

    C28x does not support byte access (only 16bit/32bit access) so these signals are optional.

    Regards,

    Vivek Singh

    Sorry it was a mistake....I wanted to say:

      For example, the pins EM1A13, EM1A14, EM1A19 and EM1A20 are [not] routed as EM1CAS,EM1RAS, EM1BA1 and EM1BA2 respectively. (However they seem to be the same GPIOXX pin).

    About EM1A14 and EM1A15 pins, I asked because you listed them in the  pin mapping you provided.

    If C28x does not support  byte access....Is there any reason to include them?

    Thank you Vivek

  • Hello Vivek.

    Did you check my previous message?

    Thank you

  • Hi,

    For example, the pins EM1A13, EM1A14, EM1A19 and EM1A20 are [not] routed as EM1CAS,EM1RAS, EM1BA1 and EM1BA2 respectively. (However they seem to be the same GPIOXX pin).

    That is correct. Though same GPIO pins, mux setting is different for SDRAM pins vs ASYNC (address) pins.

    If C28x does not support  byte access....Is there any reason to include them?

    You can choose either option. Tie them to active value on board or connect it to the EMIF pins.

    Regards,

    Vivek Singh

  • Hi, Let me know if you have any further queries on this.

    Vivek Singh
  • Thank you Vivek.
    You have been really helpful in this matter