Nintendo DMG-01 Manual - Page 34

Interrupt Descriptions

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2.12.2. Interrupt Descriptions Game BoyTM CPU Manual 2.12.2. Interrupt Descriptions The following interrupts only occur if they have been enabled in the Interrupt Enable register ($FFFF) and if the interrupts have actually been enabled using the EI instruction. 1. V-Blank The V-Blank interrupt occurs ~59.7 times a second on a regular GB and ~61.1 times a second on a Super GB (SGB). This interrupt occurs at the beginning of the V-Blank period. During this period video hardware is not using video ram so it may be freely accessed. This period lasts approximately 1.1 ms. 2. LCDC Status There are various reasons for this interrupt to occur as described by the STAT register ($FF40). One very popular reason is to indicate to the user when the video hardware is about to redraw a given LCD line. This can be useful for dynamically controlling the SCX/SCY registers ($FF43/$FF42) to perform special video effects. 3. Timer Overflow This interrupt occurs when the TIMA register ($FF05) changes from $FF to $00. 4. Serial Transfer Completion This interrupt occurs when a serial transfer has completed on the game link port. Page 34 V 1.01

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2.12.2. Interrupt Descriptions
Game Boy
TM
CPU Manual
2.12.2.
Interrupt Descriptions
The following interrupts only occur if they have been
enabled in the Interrupt Enable register ($FFFF) and
if the interrupts have actually been enabled using the
EI instruction.
1.
V-Blank
The V-Blank interrupt occurs ~59.7 times a second
on a regular GB and ~61.1 times a second on a Super
GB (SGB). This interrupt occurs at the beginning of
the V-Blank period. During this period video
hardware is not using video ram so it may be freely
accessed. This period lasts approximately 1.1 ms.
2.
LCDC Status
There are various reasons for this interrupt to
occur as described by the STAT register ($FF40). One
very popular reason is to indicate to the user when
the video hardware is about to redraw a given LCD
line. This can be useful for dynamically controlling
the SCX/SCY registers ($FF43/$FF42) to perform
special video effects.
3.
Timer Overflow
This interrupt occurs when the TIMA register ($FF05)
changes from $FF to $00.
4.
Serial Transfer Completion
This interrupt occurs when a serial transfer has
completed on the game link port.
Page 34
V 1.01