waits until ly=3
sets lyc to 5
enables lyc int
waits for int

on int:
sets lyc to 6
sets STAT to 0
jumps to 0x1000
nops til late next ly
sets STAT to 0x40
reads IF
outputs value of IF&3

late_ff41_enable_1.gbc should output 2
late_ff41_enable_2.gbc should output 0