Nintendo DMG-01 - Game Boy Console Manual page 60

2.13.1. I/O Registers
43. FFFF (IE)
Name
Contents - Interrupt Enable (R/W)
Page 60
- IE
Bit 4: Transition from High to Low of Pin
number P10-P13.
Bit 3: Serial I/O transfer complete
Bit 2: Timer Overflow
Bit 1: LCDC (see STAT)
Bit 0: V-Blank
0: disable
1: enable
TM
Game Boy CPU Manual
V 1.01