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TMS320C6678: DDR RESETn, CSn Pull up/down Required?

Part Number: TMS320C6678

Hello,

Could you please advise if external PD is required on DDRRESETz and if external PU is required on DDRCE0z?

Erez.

 

  • Erez,

    In normal operation, there is no requirement for pull-up or pull-down resistors on either DDRRESETz or DDRCE0z.  These are 'OZ' pins that are always driven except during initial device wake-up when the output pins are all HI-Z.  Once the DSP comes out of POR reset, all peripherals initialize and these pins are driven.  DDRRESETz will then be driven low until the PHY executes the SDRAM initialization process.

    We normally add a pull-down on the DDRRESETz on our EVMs to make sure that the reset input the the SDRAMs is always held at a stable level even when the DSP is held in POR reset.  This is a recommended use condition, not a requirement.

    Tom