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AM3894: [Vatech] can you explain why CS1 is not supported in AM389x

Part Number: AM3894

Hello,

 

This is Bobby Youn who are working in WPG Korea.

Our customer Vatech uses AM389x and has a question after reading document.

we can find strings below in document.

They have used CS1 in there board, because of DDR0/1 uses CS0/1.

So, they are worrying to using CS1 in there board. So they want to know possible problem if they use CS1 in AM389x. (E.g. problems between MPU operations…)

If possible, can you explain why CS1 is not supported?

 

Best Regards,

Bobby Youn,

  • Hi Bobby,

    This device only supports one CS because a second CS is not needed to fully populate the memory space available in the device memory map for DDR3.

    Using two 4Gb x16b devices on each EMIF gives a total of 2GB which the device can address using only the CS0.

    Regards,
    Pavel

  • Hello,

     

    Thank you for your support.

    I appreciate it. I understood what you saying, but I have question about errata document for AM389x yet.

    Customer has tested their memory configuration to use CS1 and tested CS1 operation using analyzer.

    They was thought there is no issue. So they want to know that what issue happens when they use CS1.

     

    Can you check memory configuration below in AM389x?

    A. Linux Memory Map

         i. EMIF0 is assign to 0x80000000 ~ 0xBFFFFFFF

         ii. EMIF1 is assign to 0xC0000000 ~ 0xFFFFFFFF

                    >>> __raw_writel(0x0, DMM_LISA_MAP__0);

                   >>> __raw_writel(0x0, DMM_LISA_MAP__1);

                   >>> __raw_writel(0x80600100, DMM_LISA_MAP__2);

                   >>> __raw_writel(0xC0600200, DMM_LISA_MAP__3);

    B. EMIF_SDCFG: 0x4B801ABA

         i. Set to use CS 0/1 both though EMIF_SDCFG register.

    C. Physical Memory Configuration.

         i. EMIF0 : 1GB

              - CS 0 : 512MB

              - CS 1 : 512MB

         ii. EMIF1 : 1GB

              - CS 0 : 512MB

              - CS 1 : 512MB

    Thanks in advance.

    Best Regards,

    Bobby Youn,

  • Bobby,

    I confirm one more time that AM389x DDR CS1 is NOT supported, DDR CS1 is NOT functional.

    Bobby Youn said:
    So they want to know that what issue happens when they use CS1.

    Most probably, the DDR chip attached to CS1 will not behave properly.

    In AM389x datasheet, section 9.3.2.3 DDR3 Interface Schematic, all references to DDR[x]_CS1 are marked as NC (Not Connected). We are only supporting one CS because it has improved margins, and a second CS is not needed to fully populate the memory space available in the device memory map for DDR3.

    Check below e2e thread:

    Regards,
    Pavel