void updateGraphicsTest(struct gameboy * gameboy)
{
//fill a frame buffer with some simple pixel data and see if it draws correctly
setLCDStatus(gameboy);
uint8_t previousMode = getCurrentMode(gameboy);
requestAnyNewModeInterrupts(gameboy, previousMode);
if (isLCDEnabled(gameboy)){
gameboy->screen.scanlineCounter += gameboy->cpu.previousInstruction.cycles;
}
else {
return;
}
if (gameboy->screen.scanlineCounter >= SCANLINE_CYCLE_TIME){
gameboy->screen.currentScanline++;
gameboy->screen.scanlineCounter = 0;
if (gameboy->screen.currentScanline == Y){
requestInterrupt(gameboy, int_vblank);
//printf("start vblank\n");
}
else if (gameboy->screen.currentScanline > (Y + NO_OF_INVISIBLE_SCANLINES)){
gameboy->screen.currentScanline = 0;
//printf("resetting scanline\n");
}
else if (gameboy->screen.currentScanline < Y){
// printf("drawing scanline %d\n", gameboy->screen.currentScanline);
drawScanline(gameboy);
}
else {
//printf("In vblank\n");
}
}
}
void Video::updateGraphics(const int &cycles, CPU &cpuTemp)
{
setLCDStatus(cpuTemp);
if (isLCDEnabled())
_scanLineCounter -= cycles;
else
return;
if (_scanLineCounter <= 0)
{
// time to move onto next scanline
_memory->directModification(LY, _memory->read(LY) + 1);
BYTE currentline = _memory->read(LY);
_scanLineCounter = 456;
// we have entered vertical blank period
if (currentline == 144)
cpuTemp.requestInterrupt(VBlank);
// if gone past scanline 153 reset to 0
else if (currentline > 153)
_memory->directModification(LY, 0x00);
// draw the current scanline
else if (currentline < 144)
drawScanLine();
}
}
void updateGraphics(struct gameboy * gameboy)
{
int cycles = gameboy->cpu.previousInstruction.cycles;
uint8_t previousMode = getCurrentMode(gameboy);
setLCDStatus(gameboy);
requestAnyNewModeInterrupts(gameboy, previousMode);
doCoincidenceFlag(gameboy);
if (isLCDEnabled(gameboy)){
gameboy->screen.scanlineCounter += cycles;
doScanline(gameboy);
}
}
void setLCDStatus(struct gameboy * gameboy)
{
//it take 456 clock cycles to draw 1 scanline
//LCD status is in mode 2 for the first 80 (search sprite attrs)
//Mode 3 is set for the next 172 (transfer to LCD driver)
//The remaining 204 are for mode 0 (hBlank)
//When the status mode is changed to 0, 1 or 2, an interrupt request occurs
//Check bit 3, 4, or 5 to see if mode interrupt 0, 1 or 2 is enabled
//when the lcd mode is disabled, the status mode must be set to 1
if (!isLCDEnabled(gameboy)){
//starting a new scan line sets the lcd status to 2
//printf("LCD isn't enabled - starting new scanline\n");
startNewScanline(gameboy);
}
else {
// printf("LCD is enabled\n");
if (isInVBlankBounds(gameboy)){
//printf("Handle vblank\n");
handleVBlank(gameboy);
}
else if (isInSpriteAttributeBounds(gameboy)){
//printf("Handle OAM\n");
handleSpriteSearch(gameboy);
}
else if (isInDriverTransferBounds(gameboy)){
//printf("handle transfer\n");
handleTransferToLCDDriver(gameboy);
}
else {
//printf("handle hblank\n");
handleHBlank(gameboy);
}
}
}
void Video::setLCDStatus(CPU &cpuTemp)
{
BYTE status = _memory->read(0xFF41);
if (!isLCDEnabled())
{
// set the mode to 1 during lcd disabled and reset scanline
_scanLineCounter = 456;
_memory->directModification(LY, 0x00);
status &= 0xFC;
status = bitSet(status, 0);
_memory->write(0xFF41, status);
return;
}
BYTE currentline = _memory->read(LY);
BYTE currentmode = status & 0x03;
BYTE mode = 0x00;
bool reqInt = false;
// If is greater we are in VBLank period
if (currentline >= 144)
{
mode = 0x01;
status = bitSet(status, 0);
status = bitReset(status, 1);
reqInt = testBit(status, 4);
}
// Else, we are drawing scanlines in panel
else
{
int mode2bounds = 456 - 80;
int mode3bounds = mode2bounds - 172;
// mode 2
if (_scanLineCounter >= mode2bounds)
{
mode = 0x02;
status = bitSet(status, 1);
status = bitReset(status, 0);
reqInt = testBit(status, 5);
}
// mode 3
else if (_scanLineCounter >= mode3bounds)
{
mode = 0x03;
status = bitSet(status, 1);
status = bitSet(status, 0);
}
// mode 0
else
{
mode = 0x00;
status = bitReset(status, 1);
status = bitReset(status, 0);
reqInt = testBit(status, 3);
}
}
// just entered a new mode so request interupt
if (reqInt && (mode != currentmode))
cpuTemp.requestInterrupt(LCD);
// check the conincidence flag
if (_memory->read(LY) == _memory->read(LYC))
{
status = bitSet(status, 2);
if (testBit(status, 6))
cpuTemp.requestInterrupt(LCD);
}
else
{
status = bitReset(status, 2);
}
_memory->write(0xFF41, status);
}
