Status Registers #0 To #9 - Yamaha V9938 Programmer's Manual

2.2. Status registers #0 to #9

The following status registers are read-only registers for VDP status reporting. Let's
consider each register.
MSB
S#0
Vertical scan interrupt flag.
7 F
Flag for 5
6 5S
the same horizontal line
Collision flag.
5 C
4...0 5SN The number of 5
MSB
S#1
Light pen.
7 FL
generated. Reset when S#1 is read.
Mouse 2.
reset when reading status register S#1
Light pen button.
6 LPS
Mouse 1.
This flag is not reset when reading status register S#1 in both set-ups
5...1 ID # The identification number of the VDP chip
Horizontal scan interrupt flag.
0 FH
R#19. If IE1 is set, interrupt is generated. FH is reset when S#1 is read
MSB
S#2
Transfer ready flag.
7 TR
next transfer. Value of 0 means that VDP is not ready
Vertical retrace flag.
6 VR
i.e. during vertical retrace plus while lower and upper borders of the
screen is drawn
Horizontal retrace flag.
5 HR
screen, i.e. when right and left borders of the screen are drawn
Color detect flag.
4 BD
specified color was detected
Display field flag.
1 EO
the second field
Command execution flag.
0 CE
a command
© 1985 ASCII CORP. / NIPPON GAKKI CO.
7 6 5
F 5S C
th
sprite.
Five (or nine in G3...G7 modes) sprites are aligned on
Two sprites have collided
th
(or 9
7 6 5
FL LPS
Is set if light pen detects light. If IE2 is set, interrupt is
Is set if second button of mouse was pressed. This flag is not
Is set when light pen button is pressed
Is set if first button of mouse was pressed
7 6 5
TR VR HR
If set to 1, indicates to the CPU that VDP is ready for
Is set during scanning of VBLANK area of the screen,
When the search command is executed, this flag is set if
If set to 0, indicates the first field. If set to 1, indicated
4 3 2
5SN
When S#0 is read, this flag is reset
th
in G3...G7 modes) sprite
4 3 2
ID #
Is set if VDP scans line specified in register
4 3 2
BD 1 1
Is set during scanning of HBLANK area of the
If set to 1, indicates that VDP is busy executing
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1 0 LSB
Status register 0
1 0 LSB
FH Status register 1
1 0 LSB
EO CE Status register 2
© 2010-2015 Eugeny Brychkov