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Question about SDRAM and the AM1707

Varun Shah
Intellectual 2470 points
Other Parts Discussed in Thread: AM1707

Hello,

What is the SDRAM capacity on the AM1707?  It looks like it has the addressing necessary for 64M addresses (16M R/C addresses x 4 banks), but they show 16 bit data path x 2 chips so that is a theoretical maximum of 128MB x 2 = 256MB (Megabytes) of SDRAM.

 

I would like to verify this because in the AM1707 datasheet they only talk about using 1 x 16MB chips (8M x 16 bit) or 2 x 32MB chips (2 chips of 16M x 16 bits) for a total of 64MB in the system, as is found on the Eval board.

 

Can we go up to 256 MB?  (2 chips of 64M x 16 bits)

 

  • 0
    TI__Genius 9490 points

    Varun,

    The datasheet table 6-24 shows supported SDRAM configurations.

    256MB is the capacity, ensure that your memory chips have the correct # of addressing lines to interface to AM1707, that is 13 address lines.

    regards,

    miguel

     

  • 0 in reply to Miguel A. Alanis
    Prodigy 130 points

    Miguel, I posed the original question through my support channels.

    I totally overlooked that table.  The capacities are very clear now.

    One remaining question:  The table says all configurations have a 32-bit data bus, but the first example in figure 6-19 portrays a 16-bit interface.  My question is, can we start out with one memory chip with a 16-bit interface, and then later expand it with a second chip on the other 16 bits, as in figure 6-21?

    My intent is to lay out the circuit according to Figure 6-21 (with two chips), but populate it at first with only one chip.  That way we can stay with one chip if our software will work with it, but be able to expand the prototype boards to two chips if the software requires it.

    Thank you for your help.

    Regards,  John

  • 0 in reply to John Haggis
    TI__Mastermind 27585 points

    The table shows both 32 and 16 bit configurations. There shouldn't be a problem with no-popping one of the memories and treating it as if there were only 1 memory on the bus.

    Jeff