|546,547|$0222,$0223|VVBLKI|Vertical Blank Immediate Register|both

VBLANK immediate register. Normally jumps to the stage one VBLANK vector NMI interrupt processor at location 59345 ($E7D1); in the new OS "B" ROMs; 59310, $E7AE). The NMI status register tests to see if the interrupt was due to a VBI (after testing for a DLI) and, if so, vectors through here to VBI the routine, which may be user-written. On powerup, VBI's are enabled and DLI's are disabled. See [VDSLST] location 512/$200.

see also: [VDSLST], [VVBLKD], [Interrupts]