Register Functions; Control Registers; Mode Registers - Yamaha V9938 Programmer's Manual

2.1. Control registers

2.1.1. Mode registers

MSB
R#0
R#1
R#8
R#9
* Indicates negative logic
Digitize mode:
R#0 DG
IE2 Enables interrupts from Light pen
IE1 Enables interrupt from horizontal retrace
M5 Screen mode flag (see Screen Modes chapter)
M4 Screen mode flag (see Screen Modes chapter)
M3 Screen mode flag (see Screen Modes chapter)
R#1 BL Blank screen: if set to 1, screen display is enabled. If set to 0, screen
display is disabled and no VRAM read operations are performed.
IE0 Enables interrupt from vertical retrace
M1 Screen mode flag (see Screen Modes chapter)
M2 Screen mode flag (see Screen Modes chapter)
Sprite size:
SI
8*8
Sprite enlarging:
MAG
Mouse:
R#8 MS
mouse. If set to 1, sets color bus into output mode and disables mouse
Light pen:
LP
TP Sets the color of code 0 to the color of the palette
Color bus:
CB
color bus into output mode
VR Selects the type and organization of VRAM. If set to 1, VRAM is 64Kx1Bit
or 64Kx4bits. If set to 0, VRAM is 16Kx1Bit or 16Kx4Bits. Affects how VDP
performs refresh on DRAM chips
Sprite disable:
SPD
are not performed.
BW Black/White: if set to 1, output is grayscale in 32 tones
© 1985 ASCII CORP. / NIPPON GAKKI CO.

2. REGISTER FUNCTIONS

#0
#32
7 6 5
0 DG IE2
0 BL IE0
MS LP TP
LN 0 S1
sets the color bus to the input or output mode
when set to 1, sprite size is 16*16. If set to 0, sprite size is
If set to 1, sprites are enlarged (double size)
when set to 1, sets the color bus into input mode and enables
when set to 1, enables light pen
when set to 1, sets color bus into input mode. If set to 0, sets
if set to 1, sprites are not displayed and related VRAM reads
to #23
to #46
4 3 2
IE1 M5 M4
M1 M2 0
CB VR 0
S0 IL E0
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1 0 LSB
M3 0 Mode R#0
SI MAG Mode R#1
SPD BW Mode R#8
*NT DC Mode R#9
© 2010-2015 Eugeny Brychkov