© 1985 ASCII CORP. / NIPPON GAKKI CO.
Page 69 of 108
© 2010-2015 Eugeny Brychkov
4.4.2. YMMM (High speed move VRAM to VRAM, Y coordinate only)
YMMM command is used to transfer data from the area specified by DX, SY, NY, DIX,
DIY and the right (or left) edge of the screen, in the Y-direction determined by DY.
Video or expansion RAM
(DX, DY)
↑↑
(DX, SY)
→
DIX
NY
↓
DIY
YMMM execution order
Step 1: Set necessary coordinates in command registers
MSB
7 6 5 4 3 2 1 0
LSB
R#34
SY7 SY6 SY5 SY4 SY3 SY2 SY1 SY0
R#35
0 0 0 0 0 0 SY9
SY8
SY: Source
transfer point Y
R#36
DX7 DX6 DX5 DX4 DX3 DX2 DX1 DX0
R#37
0 0 0 0 0 0 0
DX8
DX*: Source
transfer point X
R#38
DY7 DY6 DY5 DY4 DY3 DY2 DY1 DY0
R#39
0 0 0 0 0 0
DY9
DY8
DY: Destination
transfer point Y
R#42
NY7 NY6 NY5 NY4 NY3 NY2 NY1 NY0
R#43
0 0 0 0 0 0
NY9
NY8
NY: Number of
dots in Y-axis
*In G4 and G6 modes, the lower one bit, and in G5 mode, the lower two bits are lost in registers related to
X-coordinate (DX, NX)