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MSP432E411Y: external Flash and SDRAM

Susan Yang
Genius 9955 points

Part Number: MSP432E411Y

Dear team,

My customers want to use EPI to connect external Flash and SDRAM. They have many questions. Please help to check them.

Because customers need to use the third-party file system fatfs, they want to use its unicode encoding. They need to include a unicode array close to 2M into the program. Customers now have some questions.

Assume：MSP432 expands flash, for example, it expands 32M flash.

1. Whether the off-chip flash can save the initialized array data.

2. Can the program be executed directly from the off-chip flash.

3. Will the addressing speed of the off-chip flash be slow or the reading and writing speed will be slow?

4. I found that, for example, SDRAM and flash can be expanded to a large extent, so without considering the cost of the product, there will be any problems if the expansion is too large. In addition to the power consumption, I would like to know the impact.

5. If I need to sleep MSP432 under low power consumption, do I not use SDRAM but use SRAM, because I can power SDRAM or SRAM alone, but I cannot refresh SDRAM because MSP432 is already dormant, so I need to use SRAM, am I right?

6. Can the EPI interface expand Flash and SRAM at the same time?

Thank you!

  • +1
    TI__Expert 7015 points
    Susan Yang said:
    1. Whether the off-chip flash can save the initialized array data.

    Yes. 

    Susan Yang said:
    2. Can the program be executed directly from the off-chip flash.

    Yes. 

    Susan Yang said:
    3. Will the addressing speed of the off-chip flash be slow or the reading and writing speed will be slow?

    Please check section 16.4.1 in the EPI chapter of User's guide for detailed speed for each configuration of SDRAM, host-bus mode, general-purpose mode and general parallel GPIO mode. 

    Susan Yang said:
    4. I found that, for example, SDRAM and flash can be expanded to a large extent, so without considering the cost of the product, there will be any problems if the expansion is too large. In addition to the power consumption, I would like to know the impact.

    There is limitation for the size of SDRAM, Flash expanded due to the pins limitation for EPI module. Please check the EPI chapter of User's guide for detailed information. 

    Susan Yang said:
    5. If I need to sleep MSP432 under low power consumption, do I not use SDRAM but use SRAM, because I can power SDRAM or SRAM alone, but I cannot refresh SDRAM because MSP432 is already dormant, so I need to use SRAM, am I right?

    It is incorrect. EPI SDRAM mode has low-power self-refreshing state to working in SLEEP mode, i.e. SDRAM can be refreshed in MSP432 SLEEP mode. Please refer to section 16.4.2 in the user's guide for details. 

    Susan Yang said:
    6. Can the EPI interface expand Flash and SRAM at the same time?

    SRAM and Flash are both in EPI Host bus mode. I think it is possible if the Flash and SRAM interface is similar and timing specification can be compatible. You can use CS pins to select Flash or SRAM.