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F28M35 M3 access EPI conflict with C28 access shared memory?

Arthur Wu
Prodigy 130 points

Hi all,

We use F28M35 M3 reading from EPI device(EtherCAT slave controller), C28 read/write share memory. When M3 core read from EPI device frequently, we found C28 running slowly, why? M3 access EPI conflict with C28 access shared memory? 

  • 0
    Prodigy 130 points
    I means M3 access EPI and C28 access shared memory simultaneously.
  • 0 in reply to Arthur Wu
    TI__Guru** 116201 points

    Hi Arthur,

    M3 access to EPI and C28x access to Shared RAM are exclusive and should not have any impact on each other.

    Could it be possible that there are some handshake between M3 and C28x program due to which when M3 is accessing EPI the handshake process becomes slower hence it may appear that C28x core is running slower ?

    Regards,

    Vivek Singh

  • 0 in reply to Vivek Singh
    Prodigy 130 points
    Hi Vivek,
    Thank you for help.
    We have do double check for the issue:it did not appear again, we'll continue verifying it. Now we have another question:

    you know EPI is shared between M3 core and C28 core, If we do a design: M3 core access extended SRAM 1 by EPI, C28 core access extended SRAM2 by EPI, M3 access SRAM1 take impact C28 access SRAM2? What's the impact?

    Regards,
    Arthur
  • 0 in reply to Arthur Wu
    TI__Guru** 116201 points

    Hi Arthur,

    Arbitration between M3 and C28x access to EPI is done based on Round-Robin scheme so once access from one master completes other master access goes through. So basically impact is time taken by a master to complete current access. Does that answer your question? Let me know if you are looking for some other detail? Also it'll be good if you could share your system requirement.

    Regards,

    Vivek Singh

  • 0 in reply to Vivek Singh
    Prodigy 130 points
    Thank Vivek!
    You know F28M35 have only 32KB+34KB+64KB = 130KB SRAM, the SRAM resource limits our complex application. Some times we want to extend C28 SRAM, also we want to extend M3 SRAM, how to extend C28 SRAM and M3 SRAM? By F28M35 technical user manual, we can only use EPI to extend C28 SRAM and M3 SRAM? Is there other solution to extend SRAM?

    Regards.
    Arthur
  • 0 in reply to Arthur Wu
    TI__Guru** 116201 points
    Arthur,

    For additional RAMs you need to use the external RAM via EPI. Any reason why on chip Flash can not be used for most of your application code?

    Regards,
    Vivek Singh