Hello all,
To suppplement the project I did this summer, I'm designing a cape (that will be released soon) to fit the BeagleBone Black that provides buffering between the Bone and the user hardware. It uses a 74LVCH16245 buffer for the purpose. I had two questions: (i) Since the logic input pins are also the BOOTx pins for the AM3358 SoC, I wouldn't like the cape to kick in before the SoC boots up. The reference manual states that "no pin is to be driven till SYS_RESETn is high" . However on page 113 - "2) Do not drive any external signals into the I/O pins until after the VDD_3V3B rail is up." caused a bit of confusion in my mind as to which criteria is more important and should be satisfied in this case. The current setup for this purpose is a BSS138 that pulls the OE of the buffer low when VDD_3V3B is present. The OE pin is high otherwise. I've enclosed an excerpt of the schematic in this post. (ii) If there should be ~33 ohm resistors between the SoC I/O pins and the buffer, and between the logic inputs and the 74LVCH16245. Going through an appnote by TI I found that the 16245 integrates some form of termination on the I/O pads and think it may not be required in this case. Best Regards Abhishek -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
