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DM8168: DDR3 x16 4Mbit device support

Sven Hansson
Prodigy 30 points

Hi Forum,

According to the answers of forum question "Subject: DM8168: DDR3 Configuration" (MarcPyne quoted below) it would be possible to achieve a total DDR3 memory size of 2 GByte using 16-bit data bus width devices. As I understand this may be done by connecting one pair of 16-bit DDR3 devices in parallel to each (32-bit) EMIF, making a total of 4 DDR3 16-bit devices on the two EMIF's together, as described in the DM8168 Data Sheet (SPRS614A, p. 183, par. 8.3.2.2). (There also seems to be no possibility to connect more than 2  16-bit devices to each of the two EMIF's.)

Thus, to achieve a total of 2 GByte, i.e. 16 Gbit, with 4 devices (of the same size) each device must have a capacity of 4 Gbit.

However, the DM8168 Data Sheet (SPRS614A, p. 171, par. 8.3) also states that the maximum DDR3 device size that may be used is 2 Gbit: "Memory device capacity: 64Mb, 128Mb, 256Mb, 512Mb, 1Gb, and 2Gb devices".

In these two statements (by the Data Sheet and by MP) i see a contradiction.

Question 1: Is it really possible to use the complete 1 GByte adress space of each EMIF using 16-bit DDR3 devices (in spite of the Data Sheet statement)?

Question 2: If yes, which supported combination of 16-bit DDR3 devices may be used to connect 1 GByte of memory to one EMIF?

Question 3: Also, if the answer of Q1 is yes, which 16-bit DDR3 device sizes are supported?


Best regards,

Sven

QUOTE:
"Subject: DM8168: DDR3 Configuration
Answer:
Posted by replied on 10-20-2011 5:20 PM
Alex,
Yes, each EMIF can support up to 2 GB total address space.  For DDR3 you can use 8-bit or 16-bit devices.
Regards,
Marc
Answer:
Posted by replied on 12-16-2011 4:24 PM
Alex,
I misspoke in my answer to your first question - the total address space is 2GB, not per EMIF.
Regards,
Marc"
  • 0
    TI__Mastermind 25055 points

    Sven,

    Sorry for the confusion.  We need to clarify this in the datasheet since it does state the device only supports up to 2Gb devices.  You are correct that 4 4Gb x16b devices give a total of 2GB address space, which the device can address.  That is from the HW perspective.  There are still some discussions going on about full support in SW for 4Gb devices.

    Regards,
    Marc

  • 0 in reply to MarcPyne
    Intellectual 420 points

    Hi Marc

    We've just completed a design based on the TMS320C6A8168, using four 4Gb x 16b devices (two per DDR controller), giving a total address space of 2GByte.

    Can you confirm whether the current SW (PSP) fully supports 4Gbit devices, so we will be able to actually use all of the 2GByte RAM available on our board?

    Also, are there any differences in this respect between the C6A8168 and the DM8168? We've been blindsided by TI's decision to withdraw the C6A8168 from production and only continue with the DM8168 and we need to fully understand the implications of this on our current design. E.g., will our board work if we simply replaced the C6A8168 with the (pin compatible) DM8168?

    Regards

    Ockie

  • 0 in reply to Ockie Van Schalkwyk
    TI__Mastermind 25055 points

    Ockie,

    My understanding is that the current PSP does support 4Gb devices.   There are no differences in this respect between the C6A8168 and the DM8168; the only difference is that the DM8168 inlcudes the HDVICP2 processors for video encode/decode.  They are pin-compatible so there will be no problem with replacing the device on your board.

    Regards,
    Marc

  • 0 in reply to MarcPyne
    Expert 1850 points

    Hi Marc,

    I am also interested in same for DM8148.

    Micron is sampling a MT41K256M32 part (contains two 4Gb x 16b) that

    would allow for 1 device per EMIF and simplify placement and routing.

    Does the DM4148 PSP support the same?

    Patrick

  • 0 in reply to patrick nefos
    Expert 1850 points

    patrick nefos said:

    Sorry for mispell, DM8148 PSP is what I intended...

  • 0 in reply to patrick nefos
    TI__Mastermind 25055 points

    I believe so, but I am not totally sure.  I would recommend submitting a new post on this in the DM8148 Forum.

    Regards,
    Marc