Explanations Of Commands; Hmmc (High-Speed Move Cpu To Vram) - Yamaha V9938 Programmer's Manual

4.4. Explanation of the commands
4.4.1. HMMC (High speed move CPU to VRAM)
HMMC command is used to transfer data from the CPU to video or expansion RAM
into a specified rectangular area through VDP. When using this command, note the
limitation on the X coordinate in various modes (255 or 511).
CPU
HMMC execution order
Step 1: Set necessary coordinates in command registers
MSB
R#36
R#37
R#38
R#39
R#40
R#41
R#42
R#43
*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)
Step 2: Set color register value
The first byte transferred from CPU after starting executing the HMMC command
should be located in color register R#44 (CLR). Format of color data depends on the
graphics mode.
© 1985 ASCII CORP. / NIPPON GAKKI CO.
VDP
7 6 5
DX7 DX6 DX5
0 0 0
DY7 DY6 DY5
0 0 0
NX7 NX6 NX5
0 0 0
NY7 NY6 NY5
0 0 0
Video or expansion RAM
(DX, DY)
NY
↓
4 3 2
DX4 DX3 DX2
0 0 0
DY4 DY3 DY2
0 0 0
NX4 NX3 NX2
0 0 0
NY4 NY3 NY2
0 0 0
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NX
DIY
1 0 LSB
DX1 DX0 DX*:
Destination X
0 DX8
DY1 DY0 DY: Destination
Y
DY9 DY8
NX1 NX0 NX*: Number of
dots in X-axis
0 NX8
NY1 NY0 NY: Number of
dots in Y-axis
NY9 NY8
© 2010-2015 Eugeny Brychkov
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