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Introduced a four-cycle delay between playfield fetch and display, curing Yar's Revenge. Also disabled barrel roll scanling colouring again. I really need to make my mind up on that.

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This commit is contained in:
Thomas Harte 2016-05-16 19:55:56 -04:00
parent f19ed2e8f8
commit 4ad074fc78
3 changed files with 30 additions and 10 deletions
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34
Machines/Atari2600/Atari2600.cpp
View File

@ -80,8 +80,12 @@ Machine::~Machine()
uint8_t Machine::get_output_pixel()
{
// get the playfield pixel and hence a proposed colour
int offset = _horizontalTimer - (horizontalTimerPeriod - 160);
uint8_t playfieldPixel = _playfield[offset >> 2];
unsigned int offset = _horizontalTimer - (horizontalTimerPeriod - 160);
if(!(offset&3))
{
_playfieldPixel = _nextPlayfieldPixel;
_nextPlayfieldPixel = _playfield[(1 + (offset >> 2))%40];
}
uint8_t playfieldColour = ((_playfieldControl&6) == 2) ? _playerColour[offset / 80] : _playfieldColour;
// get player and missile proposed pixels
@ -176,7 +180,7 @@ uint8_t Machine::get_output_pixel()
}*/
// return colour
return playfieldPixel ? playfieldColour : _backgroundColour;
return _playfieldPixel ? playfieldColour : _backgroundColour;
}
// in imputing the knowledge that all we're dealing with is the rollover from 159 to 0,
@ -249,6 +253,15 @@ void Machine::output_pixels(unsigned int count)
_outputBuffer++;
}
}
else
{
// fetch this for the entire blank period just to ensure it's in place when needed
if(!(_horizontalTimer&3))
{
unsigned int offset = 4 + _horizontalTimer - (horizontalTimerPeriod - 160);
_nextPlayfieldPixel = _playfield[(offset >> 2)%40];
}
}
/* if(_horizontalTimer < (_vBlankExtend ? 152 : 160)) {
uint8_t throwaway_pixel;
@ -266,6 +279,7 @@ void Machine::output_pixels(unsigned int count)
if(!_horizontalTimer)
{
_vBlankExtend = false;
set_ready_line(false);
}
}
}
@ -277,14 +291,17 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
uint8_t returnValue = 0xff;
unsigned int cycles_run_for = 1;
// this occurs as a feedback loop — the 2600 requests ready, then performs the cycles_run_for
// leap to the end of ready only once ready is signalled — because on a 6502 ready doesn't take
// effect until the next read; therefore it isn't safe to assume that signalling ready immediately
// skips to the end of the line.
if(operation == CPU6502::BusOperation::Ready) {
unsigned int distance_to_end_of_ready = horizontalTimerPeriod - _horizontalTimer;
cycles_run_for = distance_to_end_of_ready / 3;
output_pixels(distance_to_end_of_ready);
} else {
output_pixels(3);
}
output_pixels(cycles_run_for * 3);
// if(_hMoveWillCount) {
// _hMoveCounter = 0x0f;
// _hMoveFlags = 0x1f;
@ -292,9 +309,6 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
// _hMoveWillCount = false;
// }
if(!_horizontalTimer)
set_ready_line(false);
if(operation != CPU6502::BusOperation::Ready) {
// check for a paging access
@ -558,6 +572,8 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
_piaTimerStatus |= 0xc0;
}
// output_pixels(cycles_run_for * 3);
return cycles_run_for;
}

4
Machines/Atari2600/Atari2600.hpp
View File

@ -48,6 +48,10 @@ class Machine: public CPU6502::Processor<Machine> {
uint8_t _backgroundColour;
uint8_t _playfield[40];
// playfield outputs
uint8_t _playfieldPixel; // the pixel currently being output
uint8_t _nextPlayfieldPixel; // the next pixel to be output; latched ahead of time
// player registers
uint8_t _playerColour[2];
uint8_t _playerReflection[2];

2
Outputs/CRT/Internals/Shaders/OutputShader.cpp
View File

@ -78,7 +78,7 @@ std::unique_ptr<OutputShader> OutputShader::make_shader(const char *fragment_met
"void main(void)"
"{"
"fragColour = vec4(%s, 0.5*cos(lateralVarying));"
"fragColour = vec4(%s, 0.5);"//*cos(lateralVarying)
"}",
sampler_type, fragment_methods, colour_expression);