What is the maximum DDR size that BF54x can support?


Is there an manual/data sheet error of the  size of DDR that BF54x can be

From BF54x  HRM,

* Supports industry standard double data rate (DDR SDRAM) from 64  Mbit to
512 Mbit device sizes with a configuration of x4, x8, or x16.
*  Provides 16-bit wide data interface to DDR SDRAM.
* Supports up to 256 MB of  DDR SDRAM with one external bank.

The manual said BF54x can support  up to 256MB per external bank, however,
there is another paragraph  saying that it can support up to 512Mb device which
is only 64 MB. This  description is confusing. Can we connect a 1 Gbit or
larger DDR? If not,  how can we get 256MB per external bank.


  • Hi,

    BF54x cannot support 1Gb DDR SDRAM devices.

    You can use 4 64MB SDRAM devices per external bank to get 256MB DDR  memory.

    Tables 6-6 to 6-9 in the HRM will give you the possible  configurations.


    Hope  this answers your question.


  • Hi,

       what is the minimum and maximum SDRAM size that can support by BF-533. If we have to connect 8-MB SDRAm to BF-533, what are points we have to consider.

    with regards,


  • There is a soft-limited minimum of 16MB on all Blackfin processors with SDR-SDRAM interface.

    But actually there is no hard-limit. If you SDRAM size is less than 16MB, you will have some gaps within you memory map. Lets do an example:

    SDRAM size is 8MB.

    EBIU_SDBCTL must be set to 16MB (-> minimum size) and the External Bank Column Address Width is usually 8 bits wide.

    The remaining address line(s) stay unconnected (see data sheet for more details on unused pins).

    Now the trick. The ldf-files needs to create the gapes in the memory map.

    You need four segments, representing the four internal banks:

    SDRAM_MEM_3     { TYPE(RAM) START(0x00C00000) LENGTH(0x00200000) WIDTH(8) }
    SDRAM_MEM_2     { TYPE(RAM) START(0x00800000) LENGTH(0x00200000) WIDTH(8) }
    SDRAM_MEM_1     { TYPE(RAM) START(0x00400000) LENGTH(0x00200000) WIDTH(8) }
    SDRAM_MEM_0     { TYPE(RAM) START(0x00000000) LENGTH(0x00200000) WIDTH(8) }

    When opening VisualDSP++ and the memory window, you will see that e.g. address 0x00200000 is the mirrored version of 0x00000000 and so on. Same applies to the other banks.

    This is because the "MSB"-Address line is not connected.

    For smaller SDRAM, the start addresses are the same but the length is less (alway 1/4 of the SDRAM size).

    The maximum size for SDR-SDRAM is 128MB for the ADSP-BF533.

    The ADSP-BF534/6/7 support 512MB and the ADSP-BF561 supports 128MB per external Bank.

  • Hi

    What is the maxium Size support for BF523/5/7 and what is the maximium for BF522/4/6

    Data sheet and manual is a bit confusing .

    Thanking you

  • The data sheet is pretty clear on that: 128MB. Just look at the Figure 3  Internal/External Memory Map

    The HRM is still under review and the numbers (512MB) are wrong. It is 128M for the ADSP-BF52x Blackfin processor family.

    BF51x BF52x BF531/2/3 BF534/6/7 BF538/9 BF54x BF561
    128MB 128MB 128MB 512MB 128MB 512MB 128MB
    per ext. Bank per ext. Bank