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EIM Signals and Boot Configuration

Question asked by Durmuş Kurtuluş on Aug 28, 2014
Latest reply on Aug 28, 2014 by igorpadykov

Hi all,


In our design based on SABRE SDP, we try to implement 3 configurations for boot selection:

  • eMMC via USDHC3
  • external SD/MMC card via USDHC1
  • SPI NOR flash via ECSPI1

Out of 32 EIM signals related with boot configuration, we are using only 2 in our design, specifically EIM_EB2 (E22) as SPI1_CS0 and EIM_EB3 (F23) as UART1_RI_B.

I already removed the series bus isolation resistors (4.7k) because they are not connected to anywhere, except for those two above. I have 2 questions to make sure what I did is correct:


I checked the reference manual for the related signals for boot selections. When I guarantee that the boot-up process will occur either from USDHC1, USDHC3 or ECSPI1;

1) Do I have to connect other unrelated boot signals to ground via 10k resistors? Or can I connect them directly to ground?

2) Since EIM_EB2 and EIM_EB3 are irrelevant for the mentioned boot selections, do I need any isolation or pull-down for them? (since I'm using them as low active signals, it would not be correct to pull them down)


Thanks in advance.