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Unused pins 21489

Question asked by MarcZ on Jun 26, 2013
Latest reply on Jun 27, 2013 by MarcZ



We are using the ADSP-21489 EZ-kit and we are currently designing a custom board.


I saw some posts but I still have some questions concerning the pins that are unused.


1. About the DAI/DPI. There are some confusion between some forum posts by AD and the Hardware Reference Manual.

  • The Hardware Reference Manual is mentioning (DAI Default Routing 10-24 and DPI Default Routing 10-28):

              "Note that all DAI inputs which are not routed by default are tied to signal low." (10-24)

               "All DPI input buffers which are not routed by default are driven low and all DPI pin buffer enable signals are driven low." (10-28)

              "Regardless of the system design, it is good practice to tie all unused inputs to a high or low level to reduce dynamic power consumption." (Unused                DAI/DPI Connections 10-28)

  • I've tested on my board the pins that I don't use and there are all tied high (DAIs and DPIs).
  • From a forum post (DivyaS) :

          "The internal pull-up (ipu) and internal pull-down (ipd) resistors on 214xx are designed to hold the internal path from the pins at the expected           logic levels. To pull-up or pull-down the external pads on these processors to the expected logic levels it is recommended to use external           resistors."


2. About ADDR pins. Should the address lines be tied to a certain logic level?


3. About MS pins. If we do not use /MS0, should we tie high this pin?


Please clarify these points. (Also if I should assert these pins by code or by external resistors if necessary)


Thank you for your help,