Nintendo GAME BOY Programming Manual page 68

Game Boy Programming Manual
Special Notes
!
The number of bytes transferred by the new DMA method must be specified in 16-
byte increments; byte counts that are not a multiple of 16 cannot be transferred.
!
With the new DMA transfer method, transfers are performed at a fixed rate
regardless of whether the CPU is set to operate at normal or double-speed.
!
Horizontal blanking DMAs should always be started with the LCDC on and the
STAT mode set to a value other than 00.
!
General-purpose DMAs should be performed with the LCDC off or during a vertical
blanking period.
!
When the new DMA transfer method is used to transfer data from the user program
area (0-7FFFh), mask ROM and MBC for double-speed mode are required.
1.8.3 DMA Control Register: DMG and CGB
NAME ADDRESS
DMA
BIT 7 6
FF46h
5 4 3 2 1
68
0
DMA Transfer and Starting
W
Address