Commands; Types Of Commands - Yamaha V9938 Programmer's Manual

4.1. Types of commands

Commands are used to perform specific complex operations on the video memory,
and thus on the image displayed on the screen. See the list of available commands in the
table below.
Command Destination Source Unit
name
High-speed VRAM
move
VRAM
VRAM
VRAM
Logical VRAM
move CPU
VRAM
VRAM
Line VRAM
Search VRAM
Pset VRAM
Point VDP
Invalid
Stop
*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)
The process of execution of VDP commands consists of several steps:
• Ensure that current mode is G4 – G7. In other modes result is not guaranteed
• Check the bit 0 (CE, command execution) flag in status register S#2 to be 0. If it's
1, then previous command is in progress and program needs to wait for
completion or issue STOP command
• Set necessary parameters for command execution in registers R#32 to R#45 as
necessary. It is easy to write whole the set of values to registers using indirect
register addressing mode with auto-increment turned on
• Write command code to the R#46 (CMR, command register)
• Wait till command execution is completed by checking bit 0 (CE) of S#2 to be 0
• If current command needs to be aborted, execute STOP command
© 1985 ASCII CORP. / NIPPON GAKKI CO.

4. COMMANDS

Mnemonic
CPU Byte HMMC*
VRAM YMMM*
VRAM HMMM
VDP HMMV
CPU Dot LMMC
VRAM LMCM
VRAM LMMM
VDP LMMV
VDP LINE
VDP SRCH
VDP PSET
VRAM POINT
STOP
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CM3 CM2 CM1
1 1 1
1 1 1
1 1 0
1 1 0
1 0 1
1 0 1
1 0 0
1 0 0
0 1 1
0 1 1
0 1 0
0 1 0
0 0 1
0 0 1
0 0 0
0 0 0
© 2010-2015 Eugeny Brychkov
CM0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0