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Unused Pins on the DDR2 Interface

Jon Jensen
Prodigy 90 points
Other Parts Discussed in Thread: TMS320C6472

The C6472 datasheet gives the option of using 1 x16 DDR2 device. The appnote spraat7d does not give any guidance to using just one device. My main concern is how should we connect the unused pins?

These pins would include the higher 2 bytes for the chip select, mask, data strobe, data strobe gate, and data bits.

  • 0
    TI__Mastermind 42545 points

    This issue is discussed in section 6.9.1 of the TMS320C6472/TMS320TCI6486 Hardware Design Guide (SPRAAQ4B-October 2009) which states the following.

    "If the DDR2 is operated in 16-bit mode, the upper DDR2 bi-directional pins should be pulled to valid states. BSDDQS2P, BSDDQS3P, and BED[31:16] should have pull-up resistors to DVDD18. BSDDQS2N and BSDDQS3N should have pull-down resistors to GND. BSDDQM2 and BSDDQM3 can be left not connected."

  • 0 in reply to Bill Taboada
    Prodigy 90 points

    You think we can leave BSDDQGATE2 and 3 disconnected as well?

  • 0 in reply to Jon Jensen
    TI__Mastermind 42545 points

    BSDDQGATE2 and 3 are not used when the part is configured for 16bit SDRAM operation but to avoid the need to terminate these signals it is simpler to just connect them together.  Since they are not used to determine timing this connection can be made directly under the part.  There is no need to route the trace to the memory on the board.