Does the DIR_BT_DIS apply to all external memory boot instances (e.g. FlexSPI NOR) or just enhanced Direct Memory Access? In other words if it is set, then booting from any external memory is disabled?
The reference manual doesn't provide much detail about this efuse. It refers to "NXP reserved modes" in one section, but also in the SRC_SBMR2 section has: "DIR_BT_DIS shows the state of the DIR_BT_DIS fuse. See Chapter 5, Fusemap for additional information on this fuse." Chapter 5 is "Enhanced Direct Memory Access".