waits for ly 141
enables lycint
sets lyc to 143
enables vblank int
interrupt enable

on lycint:
jumps to 0x1000
ei
does a bunch of nops
reads IF
outputs value of IF&3

on vblankint:
ret

lycint_vblankintirq_1.gb should output 1
lycint_vblankintirq_2.gb should output 0