How fast are you running the GPMC? Why are you using the clock?
Gerald On Wed, Sep 23, 2015 at 3:36 PM, <[email protected]> wrote: > I am working on a design where the BBB configures an FPGA using the GPMC > interface. > We find that this configuration fails perhaps one out of ten times. > When we probe the signals, we see a large glitch developed on the clock > line, and suspect that this is occasionally being caught as an extra edge > by the FPGA and corrupting the configuration data. > > It seems that there are two likely contributors to this problem: > 1. Our board design has long traces from the BBB to the FPGA and we are > violating the capacitive load limits for the uP's IO pins. > While the IO pins are specified to produce 6 mA output current, the > rise and fall times we measure are consistent with something more like 20 > mA being sourced/sunk during each transition of the data pins. > > 2. The BBB's P8 header has only 2 ground pins to support a 16-bit parallel > data bus. > This leads to a possibility for inductive coupling between the data > lines and the clock line (for example). > Of course this is made worse by our design having excess load > capacitance resulting in larger current transients. > > Has anyone experienced similar issues? > Does my analysis of the likely root cause make sense? > Does anyone know of a reference design showing buffering on the GPMC > signals to avoid this kind of issue? > > Thanks, > > Matt > > -- > 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. > -- Gerald [email protected] http://beagleboard.org/ -- 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.
