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How do I put DM6446 EMIF bus in high-Z mode?

Juan Gonzales
Mastermind 37340 points

 

1) Tie AEAW[4:0] signals accordingly in hardware

2) After device reset, make sure you do not enable EMIF pins via PINMUX0 settings

 Also, keep in mind that if no devices are connected to EMIF bus, it is better to pull corresponding pins low or high then to leave them floating in high-Z mode, which consumes more power and can lead to noise.

  • 0
    Prodigy 20 points

    Are there any options for disabling the bus once it has already been setup and used?  

     I need to allow another device to access a piece of flash on the EMIF bus.  From the documentation it sounds like the DaVinci is not able to release the bus properly.

  • 0 in reply to Ben Roscoe
    TI__Mastermind 37340 points

    I just checked with our hardware team; it appears you will need to use an external bus switch.

  • 0 in reply to Juan Gonzales
    TI__Mastermind 30120 points

    - The PSC module can put EMIFA pins in their default RESET state during the complete period the module is in SwRstDisable state.
    See section 7.3 of SPRUE14A.

    - But not all pin will be in HiZ during RESET. This is documented at page 102 of the DM6446 datasheet - SPRS283F.
    You can see for example that:
     - CS3 is part of the High Group so it will be kept to 1
     - EM_D[15:0] should be in HiZ since they are in the Z/Invalid Group
     - CS4 should should be in HiZ since it is in the Z group

    So the bottom line is that only part of the EMIF can be put in HiZ via the PSC. To will need to use external buffers to isolate completely the EMIF pins from the external device.