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.

Components/6560/6560.cpp

@@ -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()
 {
-	/*
+	// determine output state; colour burst and sync timing are currently a guess
-		Per http://tinyvga.com/6561 :
+	if(_horizontal_counter > 61) _this_state = State::ColourBurst;
-
+	else if(_horizontal_counter > 57) _this_state = State::Sync;
-		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;
 	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;
+		}
+	}
 }

Components/6560/6560.hpp

@@ -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);
 };
 
 }