11.12 Interrupt Compatibility
When the MVECEN bit is cleared, the IVT feature is disabled and interrupts are compatible with previous high performance 8-bit PIC18 microcontroller devices. In this mode, the IVT priority has no effect.
When IPEN is also cleared, the interrupt priority feature is disabled and interrupts are compatible with PIC16 microcontroller midrange devices. All interrupts branch to address 0008h, since the interrupt priority is disabled.