I have PCB design that incorporates two BeagleBone Blacks in a primary/standby configuration. Both BeagleBones boot from eMMC, and boot from SD when an SD card is present. For redundancy purposes, I need to be able to boot to eMMC if the SD card fails. The PCB design allows me to control the power and reset of BB1 from BB2, and BB2 from BB1. On both BeagleBones, Pin P8-10 is configured to be a GPIO (Mode 7), and Pin P8-43 is configured to be Mode 0. Pin P8-10 on BB1 is connected to Pin P8-43 on BB2, and vice versa. With an SD inserted into BB1, I am attempting to see any boot behavior changes in BB1 by setting P8-10 on BB2 either high or low. When I do this, I power down BB1 from BB2 and hold BB1’s reset low, set P8-10 on BB2 to be either high or low, then release power and then the reset on BB1. I witness no change in behavior. Am I missing something or not understanding the purpose P8-43? P8-43 in Mode 0 is supposed to be LCD_DATA2 / SYS_BOOT2, which from my reading should behave just like pushing S2.