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TMS320F28335 SRAM

Paul Joseph
Expert 2795 points


The 28335 DSP does not support enough SRAM memory.  I need to have 16MBytes available, the DSP can only go up to 4 MB.  Any suggestions please.

  • 0
    Prodigy 60 points

    Use some of the GPIO as bank select lines and have those operate as part of the chip select for the RAM devices. Yes there will be a time penality when switching banks and the logistics will get complicated.

  • 0 in reply to Peter Sauermilch
    Expert 2795 points

    Do you know if TI has any application notes or code that suggests how to bank using the DSP? 

    Thanks

  • 0 in reply to Paul Joseph
    Prodigy 60 points

    No, I don't; but it's not a difficult thing to do. I did it a lot during the days of 4 bit micros. If you are striving for a design with no additional glue logic, you will need a SRAM that has more enablement lines than the F28335 has as outputs for XINF memory control. Dedicate some GPIO lines to those other SRAM chip slect lines. That all depends on the SRAM you have selected. Then, make all your external RAM transactions through a routine the you create that insures the proper physical chip is selected using the GPIO for the logical data adderss. The disign I am currently working on originally had that as a feature but was deemed unessary. You should keep in mind several down sides. First, a lot of memory means a lot of signalling traces on a PCB and you could be put in a position of having to buffer. You could not decide about that until you have tested your PCBs. That means a lot of pain. Also, this approach is intrinsically slower than a less obtuse design. As you are forced into this by available hardware, you play the cards you are delt. Good luck.

  • 0 in reply to Peter Sauermilch
    Prodigy 175 points

    Hello,

    We are actually using the following

    xzcs6  and  xzcs7 are given to the PSARAM chip select signal and xzcs6 is also given to A20 of PSRAM by inverting its data(To create extar address line--> to access extra memory on PSRAM) .

    Now after this hardware arrangements also.. we are able to access only Zone6 and Zone7 area(ie. 1MBX16) and not more than that .

    Because, Zones are memory mapped in TIDSP ..and we cannot access beyond that...in my opinion to do that we need memory manager which will access those extra bytes

    Please Let me know ..if any one able to solve this issue..

     

    Regrads,

    Vishwa