uk.co.javagear
Class Vdp

java.lang.Object
  uk.co.javagear.Vdp

public final class Vdp
extends java.lang.Object

SMS and GG VDP Emulation.

Version:

18th January 2003

Author:

Copyright (C) 2002-2003 Chris White

See Also:

"JavaGear Final Project Report"

Field Summary

private boolean[]	bgPriority Background priorites.
private int	commandByte Command word first byte latch.
private int	counter Vertical line interrupt counter.
private int[]	cRam Colour RAM.
private int[]	display Pointer to current display.
private int[]	display1 Frame 1.
private int[]	display2 Frame 2.
private boolean	displayBackgroundLayer Generate background layer.
private boolean	displaySpriteLayer Generate sprite layer.
private boolean	firstByte First or second byte of command word.
private boolean	frameint Frame interrupt pending.
private static int[]	GG_JAVA1 GG Colours.
private static int[]	GG_JAVA2
private InterruptLine	irq Connection to Z80 interrupt line.
private int	line Current line number.
private boolean	lineint Line interrupt pending.
private int	location Location in VRAM.
private boolean	ntsc NTSC/PAL.
private int[]	oldDisplay Pointer to previous frame.
private int	operation Store type of operation taking place.
private int	readBuffer Buffer VRAM reads.
private Setup	setup Pointer to general parameters.
private static int[]	SMS_JAVA SMS Colours converted into Java RGB for speed purposes.
private boolean[]	spritecol Sprite collisions.
private int	status Status Register.
private int[]	vdpreg VDP Registers.
private byte[]	vRam Video RAM.

Constructor Summary

Vdp(Setup set, InterruptLine i)
Vdp Constructor.

Method Summary

private void	blankColumn(int lineno) Deprecated. now, faster fillRect method used.
int	controlRead() Read VDP control port (0xBF).
void	controlWrite(int value) Write to VDP control port (0xBF).
int	dataRead() Read VDP data port (0xBE).
void	dataWrite(int value) Write to VDP data port (0xBE).
private void	drawBg(int lineno) Render line of background layer.
private void	drawBGColour(int lineno) Draw a line of the current background colour.
void	drawLine(int lineno) Render line of SMS/GG display.
private void	drawSprite(int lineno) Render line of sprite layer.
void	flagChanges(boolean[] pixelUpdate) Compare this frame with the previous frame, and flag what lines have been changed.
int	getCounter() Get line interrupt counter.
int[]	getDisplay() Returns the value of property display.
boolean	getFrameIntPending() Get frame interrupt pending flag.
boolean	getIrqStatus() Get interruptLine status.
boolean	getLineIntPending() Get line interrupt pending flag.
int	getLineNo() Get line number under generation.
int	getReg(int index) Get a VDP register.
boolean	getSpriteOverflow() Get sprite overflow status.
int	getVCount() Read vertical port.
void	interrupts(int lineno) Generate VDP interrupts.
private void	plotSpritePixel(int x, int y, int location, int address, int bit) Plot single sprite pixel.
void	reset() Reset VDP.
void	setBackgroundLayer() Toggle background layer generation on/off.
void	setDisplay(int[] display) Sets the value of property display.
void	setNTSC(boolean b) Set NTSC / PAL VDP Mode.
void	setSpriteLayer() Toggle Sprite Layer Generation On/Off.
private int	unsigned(byte b) Unsign an integer.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

irq

private InterruptLine irq

Connection to Z80 interrupt line.

setup

private Setup setup

Pointer to general parameters.

vRam

private byte[] vRam

Video RAM.

cRam

private int[] cRam

Colour RAM.

vdpreg

private int[] vdpreg

VDP Registers.

status

private int status

Status Register.

firstByte

private boolean firstByte

First or second byte of command word.

commandByte

private int commandByte

Command word first byte latch.

location

private int location

Location in VRAM.

operation

private int operation

Store type of operation taking place.

readBuffer

private int readBuffer

Buffer VRAM reads.

line

private int line

Current line number.

counter

private int counter

Vertical line interrupt counter.

lineint

private boolean lineint

Line interrupt pending.

frameint

private boolean frameint

Frame interrupt pending.

bgPriority

private boolean[] bgPriority

Background priorites.

spritecol

private boolean[] spritecol

Sprite collisions.

display

private int[] display

Pointer to current display.

oldDisplay

private int[] oldDisplay

Pointer to previous frame.

display1

private int[] display1

Frame 1.

display2

private int[] display2

Frame 2.

displayBackgroundLayer

private boolean displayBackgroundLayer

Generate background layer.

displaySpriteLayer

private boolean displaySpriteLayer

Generate sprite layer.

ntsc

private boolean ntsc

NTSC/PAL.

SMS_JAVA

private static final int[] SMS_JAVA

SMS Colours converted into Java RGB for speed purposes.

GG_JAVA1

private static final int[] GG_JAVA1

GG Colours.

GG_JAVA2

private static final int[] GG_JAVA2

Constructor Detail

Vdp

public Vdp(Setup set,
           InterruptLine i)

Vdp Constructor.

Parameters:

set - pointer to general parameters

i - pointer to Z80 interrupt line

Method Detail

reset

public void reset()

Reset VDP.

setNTSC

public void setNTSC(boolean b)

Set NTSC / PAL VDP Mode.

Parameters:

b - true if NTSC, false if PAL.

getDisplay

public int[] getDisplay()

Returns the value of property display. The pointer to the current display.

Returns:

the value of property display.

setDisplay

public void setDisplay(int[] display)

Sets the value of property display. The pointer to the current display.

Parameters:

display - the new value of property display.

setBackgroundLayer

public void setBackgroundLayer()

Toggle background layer generation on/off.

setSpriteLayer

public void setSpriteLayer()

Toggle Sprite Layer Generation On/Off.

getReg

public int getReg(int index)

Get a VDP register.

Parameters:

index - index of register.

Returns:

register data.

getLineNo

public int getLineNo()

Get line number under generation.

Returns:

line number.

getCounter

public int getCounter()

Get line interrupt counter.

Returns:

line interrupt counter.

getLineIntPending

public boolean getLineIntPending()

Get line interrupt pending flag.

Returns:

true if pending.

getFrameIntPending

public boolean getFrameIntPending()

Get frame interrupt pending flag.

Returns:

true if pending.

getIrqStatus

public boolean getIrqStatus()

Get interruptLine status.

Returns:

true if pending.

getSpriteOverflow

public boolean getSpriteOverflow()

Get sprite overflow status.

Returns:

true if overflow has occurred.

getVCount

public int getVCount()

Read vertical port.

Returns:

VCounter value

controlWrite

public void controlWrite(int value)

Write to VDP control port (0xBF).

Parameters:

value - value to write.

controlRead

public int controlRead()

Read VDP control port (0xBF).

Returns:

copy of status register.

dataWrite

public void dataWrite(int value)

Write to VDP data port (0xBE).

Parameters:

value - value to write

dataRead

public int dataRead()

Read VDP data port (0xBE).

Returns:

buffered read from VRAM

interrupts

public void interrupts(int lineno)

Generate VDP interrupts. Assert the IRQ line as necessary for a particular scanline.

Parameters:

lineno - line to check for interrupts.

drawLine

public void drawLine(int lineno)

Render line of SMS/GG display.

Parameters:

lineno - line number to render.

drawSprite

private void drawSprite(int lineno)

Render line of sprite layer.

Parameters:

lineno - line number to render.

plotSpritePixel

private void plotSpritePixel(int x,
                             int y,
                             int location,
                             int address,
                             int bit)

Plot single sprite pixel.

Parameters:

x - x coordinate of pixel (for location array).

y - y coordinate of pixel.

location - coordinates to plot pixel at x+(y*256).

address - VRAM address of pixel plane.

bit - bit of plane to plot.

drawBg

private void drawBg(int lineno)

Render line of background layer.

Parameters:

lineno - line number to render.

drawBGColour

private void drawBGColour(int lineno)

Draw a line of the current background colour.

Parameters:

lineno - line number to render.

blankColumn

private void blankColumn(int lineno)

Deprecated. now, faster fillRect method used.

Blank leftmost column of a particular line.

Parameters:

lineno - line number to render.

unsigned

private int unsigned(byte b)

Unsign an integer.

Parameters:

b - value to unsign.

Returns:

unsigned value.

flagChanges

public void flagChanges(boolean[] pixelUpdate)

Compare this frame with the previous frame, and flag what lines have been changed.

Parameters:

pixelUpdate - array to flag changes in.