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AM38xx DDR Memory Size

Rinzai Bell
Intellectual 605 points
Other Parts Discussed in Thread: AM3894

I am going thru the TI AM3894 datasheet and Tech ref. manual to figure out the size and config. of the system memory (DDR3) that we can have. I have the following question :

Page 117 of the Tech reference manual section 1.2.9 Host ARM Address Map shows “Reserved (EMIF0 / EMIF1 CS1)”.

Does that mean we cannot have memory devices on CS1 of the DDR controllers ?

Does it also mean that AM3894 only supports 1GB external memory ?

  • 0
    TI__Mastermind 25055 points

    Hello,

    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.  Please refer to the updated device errata as well.

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

    Regards,
    Marc

  • 0 in reply to MarcPyne
    Prodigy 140 points

    Marc,

    Thanks a lot.

    The AM3984 datasheet section 8.3 does not list the 4Gb devices. (see below)

    Please let me know if they are supported.

    Thx

    Vishy

    From Page 154 of the datasheet:

    Memory device capacity: 64Mb, 128Mb, 256Mb, 512Mb, 1Gb, and 2Gb devices

  • 0 in reply to Vishy Canadam
    Prodigy 140 points

    Marc,

    The latest AM3894 datasheet (Rev C) does include the 4Gb devices.

    So, per you answer, a 2GB system can be setup as follows :

    DDR 1 --- CS0 ------ 1GB

    DDR 2 --- CS0 ------ 1GB

    From an ARM point of view, don't we still need the address range (0xC000_0000 - 0xFFFF_FFFF) to address the 2nd GB ?

    The datasheet and the tech ref. manual differ in terms of the address space explanantion. The address space (0xC000_0000 - 0xFFFF_FFFF) is shown as reserved in the tech ref manual. Please see below.

    Datasheet Page 28 shows:

    DDR EMIF0/1           0x8000 0000      0xBFFF FFFF         1GB         DDR

    DDR EMIF0/1           0xC000 0000     0xFFFF FFFF          1GB         DDR

    Tech. Ref. Manual page 117 shows :

    EMIF0 / EMIF1 CS0                              0x8000_0000     0xBFFF FFFF         1GB 

    Reserved (EMIF0 / EMIF1 CS1)           0xC000_0000     0xFFFF FFFF         1GB 

     

    Please let me know what you think

    Thx

    Vishy

  • 0 in reply to Vishy Canadam
    TI__Mastermind 25055 points

    Hello,

    The DS is correct.  I will make sure the TRM gets corrected.

    Thanks,
    Marc