• State Resolved
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 31 subscribers
  • Views 93 views
  • Users 0 members are here
Support feedback
Options
Options
Related

AM263P4: Interfacing an external RAm through the OSPI port

michele sponchiado
Prodigy 60 points
Part Number: AM263P4


Hi, I wonder if an external RAM chip could interface the AM263P4 through the OSPI interface, e.g. an Infineon PSRAM with xSPI octal interface and 3V operating voltage could theoretically work?

Best regards

 

  • 0
    TI__Intellectual 840 points

    Hi Michele,

    Yes, you can interface an external PSRAM (such as the Infineon PSRAM with xSPI octal interface) to the AM263P4 through the OSPI interface. However, there are some important hardware considerations to keep in mind:

    Key Hardware Considerations:

    1. DQS Line Configuration:

      • The DQS (Data Strobe) line must be pulled low when not in use
      • This is because the same DQS line serves a dual purpose: it functions as a data mask signal during write operations to the PSRAM
      • Ensure proper pull-down resistor placement in your hardware design

    2. Chip Select (CS) Pin Placement:

      • There is a difference in the ball array configuration between OSPI Flash and PSRAM, specifically in the CS pin location
      • The PSRAM CS pin placement differs from the standard Flash configuration
      • If using TI EVM: The hardware already includes provisions for selecting the appropriate CS for PSRAM operation (typically through mounting and unmounting resistors)
      • If designing custom hardware: Ensure your PCB layout accounts for the correct CS pin mapping for PSRAM devices

    Best Regards,
    Mayank Shadwani

  • 0 in reply to Mayank Shadwani
    Prodigy 60 points

    Hi, Mayank !

    Many thanks for your reply!

    If I understand correctly:

    • during write transfer, DQS acts for the PSRAM as an input data mask
    • but for the AM263Px DQS is input only, it is never driven as an output
    • so we have to pull it down to avoid unintended masking during write transfer to the PSRAM

    I see that in the schematics of the AM263P Launchpad the DQS is pulled high:

    while in the AM263P technical reference manual spruj55d, it is suggested to use a pull down on it:

    13.3.2.2.5.4.2.1.4 External Pull Down on DQS
    Per the OSPI protocol, the FLASH device drives DQS while CS is asserted. When CS is not asserted the FLASH
    device presents HiZ on DQS. When configured to use DQS, the controller uses the DQS as a clock, which
    samples the incoming data into a FIFO. Noise on the DQS when it is HiZ can cause spurious false triggering of
    the FIFO and filling it with invalid data. There is no way to clear this data except to reset the OSPI module.
    To avoid this issue, it is recommended to add a pull down on the DQS line.

    ¿So I wonder if

    • there is a specific reason for the pull-up in the Launchpad schematics instead of a pull-down
    • a pull down on DQS could work OK too in a board where both a PSRAM and an OSPI chip are connected to the TI OSPI interface (with different CSs)

    Many thanks again

    Michele

  • +1 in reply to michele sponchiado
    TI__Intellectual 840 points

    Hi Michele,

    Thank you for your detailed questions regarding the DQS signal configuration. Let me address each of your points:

    Yes, your understanding of the DQS functionality is accurate:

    • During write transfers, DQS acts as an input data mask for the PSRAM
    • For the AM263Px, DQS is input only and is never driven as an output by the controller
    • A pull-down resistor ensures a logic '0' is present on the DQS/DM line during write operations to avoid unintended data masking

    Launchpad Pull-Up Configuration

    You correctly observed that the AM263P LaunchPad uses a pull-up configuration, which differs from the Technical Reference Manual recommendation. The pull-up configuration on the LaunchPad was intentionally implemented to provide hardware with all possible configurations for evaluation and testing purposes. This allows developers to test different scenarios during the development phase.

    However, for the AM263P Control Card, we use a pull-down configuration, and everything works fine with that setup as well, which aligns with the TRM recommendation.

    michele sponchiado said:
    a pull down on DQS could work OK too in a board where both a PSRAM and an OSPI chip are connected to the TI OSPI interface (with different CSs)

    The AM263P LaunchPad does not have provisions for connecting both Flash and PSRAM simultaneously using two separate chip selects. The board features a single OSPI memory slot that supports either a Flash or a PSRAM device at one time.

    For custom board designs where you plan to connect both Flash and PSRAM to the OSPI interface using different chip selects, a pull-down resistor on DQS will work correctly for both device types. However, please note the following important consideration:

    • Pin assignment differences: Flash and PSRAM devices often have different pinouts. Carefully review the datasheets and ensure proper signal routing for both devices.

    Please let me know if you need any further clarification or have additional questions.

    Best regards,
    Mayank Shadwani