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Connect external RAM via EPI

Jianyi Bao
Expert 2220 points

I am using TivaC 1294, which has 256K internal SRAM. However, we need more RAM, so we want to add an external RAM of size about 2M or 4M bytes via EPI.


According to the datasheet, EPI can support SDRAM, SRAM and PSRAM. However, I couldn't find any reference design (schematic, code example) about them.


So could anybody tell me where to find reference design and code example?


I think PSRAM/SRAM should be my favourite verus SDRAM, but any suggestion is appreciated.
Thanks

  • 0
    TI__Guru**** 244400 points

    Hello Jianyi

    In the data sheet for TM4C129, the EPI chapter has a section called "Host Bus 16-bit Muxed Interface" which shows example schematic for connecting EPI to external SRAM. It is not complete as external address latch is required but I can prescribe some devices. Also we can help build the code.

    For the EK-TM4C129 we are doing an external memory extender with Flash+SRAM.

    http://e2e.ti.com/support/microcontrollers/tiva_arm/f/908/t/375055.aspx

    Your opinion would be useful as well.

    Regards

    Amit

  • 0 in reply to Amit Ashara
    Expert 2220 points

    Thanks. It seems that ADMux SRAM(PSRAM) must be used if we don't want to use external latcher while we want 2M bytes. Could you please recommend us some SRAM/PSRAM devices?

    I don't know if SDRAM is much more difficut from the perspective of a software programmer. Could you please comment?

    Power consumption and speed is not critical for our application.

    Thanks

  • 0 in reply to Jianyi Bao
    TI__Guru**** 244400 points

    Hello Jianyi Bao,

    We have used the following parts for testing these interfaces

    SRAM: CY62167EV30LL

    PSRAM: MT45W8MW16BGX

    SDRAM: MT48LC32M16A2TG

    Using a SDRAM I believe is far much simpler than using a PSRAM, irrespective of the power or performance requirement, since it is a dedicated mode of the EPI controller and requires minimum user configuration.

    Regards

    Amit

  • 0 in reply to Amit Ashara
    Expert 2220 points

    Thanks.

    We now plan to use "MT48LC4M16A2", which is used in a daughter board for Stellaris® LM3S9D96 Development Kit. We take it as a reference design.