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Without yet figuring out what vertical sync is meant to do, moved just about far enough forwards to see _something_ that hopefully I can soon discern characters within.

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This commit is contained in:
Thomas Harte 2016-06-05 18:02:49 -04:00
parent 444d3b69b6
commit 79e05a2413
2 changed files with 87 additions and 24 deletions
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102
Components/6560/6560.cpp
View File

@ -38,7 +38,7 @@ MOS6560::MOS6560() :
_crt->set_rgb_sampling_function(
"vec3 rgb_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate)"
"{"
"return vec3(1.0);"
"return vec3(texture(sampler, coordinate).r / 15.0);"
"}");
}
@ -71,6 +71,11 @@ void MOS6560::set_register(int address, uint8_t value)
break;
case 0xf:
if(_this_state == State::Border)
{
output_border(_cycles_in_state * 4);
_cycles_in_state = 0;
}
_invertedCells = !!((value >> 3)&1);
_borderColour = value & 0x07;
_backgroundColour = value >> 4;
@ -83,31 +88,21 @@ void MOS6560::set_register(int address, uint8_t value)
}
}
void MOS6560::output_border(unsigned int number_of_cycles)
{
uint8_t *colour_pointer = _crt->allocate_write_area(1);
if(colour_pointer) *colour_pointer = _borderColour;
_crt->output_level(number_of_cycles);
}
uint16_t MOS6560::get_address()
{
/*
Per http://tinyvga.com/6561 :
The basic video timing is very simple. For
every character the VIC-I is about to display, it first fetches the
character code and colour, then the character appearance (from the
character generator memory). The character codes are read on every
raster line, thus making every line a "bad line". When the raster
beam is outside of the text window, the videochip reads from $001c for
most time. (Some videochips read from $181c instead.) The address
occasionally varies, but it might also be due to a flaky bus. (By
reading from unconnected address space, such as $9100-$910f, you can
read the data fetched by the videochip on the previous clock cycle.)
*/
State this_state;
// random guesses; who knows?
if(_horizontal_counter > 61) this_state = State::ColourBurst;
else if(_horizontal_counter > 57) this_state = State::Sync;
// determine output state; colour burst and sync timing are currently a guess
if(_horizontal_counter > 61) _this_state = State::ColourBurst;
else if(_horizontal_counter > 57) _this_state = State::Sync;
else
{
this_state = (_column_counter >= 0 && _row_counter >= 0) ? State::Pixels : State::Border;
_this_state = (_column_counter >= 0 && _row_counter >= 0) ? State::Pixels : State::Border;
}
_horizontal_counter++;
@ -139,10 +134,71 @@ uint16_t MOS6560::get_address()
}
else if(_horizontal_counter == _first_column_location) _column_counter = 0;
// update the CRT
if(_this_state != _output_state)
{
switch(_output_state)
{
case State::Sync: _crt->output_sync(_cycles_in_state * 4); break;
case State::ColourBurst: _crt->output_colour_burst(_cycles_in_state * 4, 0, 0); break;
case State::Border: output_border(_cycles_in_state * 4); break;
case State::Pixels: _crt->output_data(_cycles_in_state * 4, 1); break;
}
_output_state = _this_state;
_cycles_in_state = 0;
pixel_pointer = nullptr;
if(_output_state == State::Pixels)
{
pixel_pointer = _crt->allocate_write_area(260);
}
}
_cycles_in_state++;
// compute the address
if(_this_state == State::Pixels)
{
/*
Per http://tinyvga.com/6561 :
The basic video timing is very simple. For
every character the VIC-I is about to display, it first fetches the
character code and colour, then the character appearance (from the
character generator memory). The character codes are read on every
raster line, thus making every line a "bad line". When the raster
beam is outside of the text window, the videochip reads from $001c for
most time. (Some videochips read from $181c instead.) The address
occasionally varies, but it might also be due to a flaky bus. (By
reading from unconnected address space, such as $9100-$910f, you can
read the data fetched by the videochip on the previous clock cycle.)
*/
// TODO: increment this address
if(_column_counter&1)
return _character_cell_start_address + _character_code*8;
else
return _video_matrix_start_address;
}
return 0x1c;
}
void MOS6560::set_graphics_value(uint8_t value, uint8_t colour_value)
{
if(_this_state == State::Pixels)
{
if(_column_counter&1)
{
// TODO: output proper pixels here
if(pixel_pointer)
{
*pixel_pointer = (uint8_t)rand();
pixel_pointer++;
}
}
else
{
_character_code = value;
_character_colour = colour_value;
}
}
}

9
Components/6560/6560.hpp
View File

@ -39,7 +39,14 @@ class MOS6560 {
enum State {
Sync, ColourBurst, Border, Pixels
};
} _this_state, _output_state;
unsigned int _cycles_in_state;
uint8_t _character_code, _character_colour;
uint8_t *pixel_pointer;
void output_border(unsigned int number_of_cycles);
};
}