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Begin process of meaningful naming.

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This is in part for readability, but primarily because the differences in VGA/EGA register definitions are better handled at set rather than during execution.
This commit is contained in:
Thomas Harte
2024-01-08 15:35:44 -05:00
parent 0cfd29fafc
commit 8290220657
1 changed files with 33 additions and 6 deletions
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39
Components/6845/CRTC6845.hpp
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@@ -56,6 +56,10 @@ enum class Personality {
EGA, // Extended EGA-style CRTC; uses 16-bit addressing throughout. EGA, // Extended EGA-style CRTC; uses 16-bit addressing throughout.
}; };
constexpr bool is_egavga(Personality p) {
return p >= Personality::EGA;
}
// https://www.pcjs.org/blog/2018/03/20/ advises that "the behavior of bits 5 and 6 [of register 10, the cursor start // https://www.pcjs.org/blog/2018/03/20/ advises that "the behavior of bits 5 and 6 [of register 10, the cursor start
// register is really card specific". // register is really card specific".
// //
@@ -99,8 +103,23 @@ template <class BusHandlerT, Personality personality, CursorType cursor_type> cl
} }
void set_register(uint8_t value) { void set_register(uint8_t value) {
switch(selected_register_) {
case 0: layout_.horizontal.total = value; break;
case 1: layout_.horizontal.displayed = value; break;
case 2: layout_.horizontal.start_blank = value; break;
}
static constexpr bool is_ega = is_egavga(personality);
static constexpr uint8_t masks[] = { static constexpr uint8_t masks[] = {
0xff, 0xff, 0xff, 0xff, 0x7f, 0x1f, 0x7f, 0x7f, 0xff, // Horizontal total.
0xff, // Horizontal display end.
0xff, // Start horizontal blank.
0xff, //
// EGA: b0–b4: end of horizontal blank;
// b5–b6: "Number of character clocks to delay start of display after Horizontal Total has been reached."
is_ega ? 0xff : 0x7f, // Start horizontal retrace.
0x1f, 0x7f, 0x7f,
0xff, 0x1f, 0x7f, 0x1f, 0xff, 0x1f, 0x7f, 0x1f,
uint8_t(RefreshMask >> 8), uint8_t(RefreshMask), uint8_t(RefreshMask >> 8), uint8_t(RefreshMask),
uint8_t(RefreshMask >> 8), uint8_t(RefreshMask), uint8_t(RefreshMask >> 8), uint8_t(RefreshMask),
@@ -133,7 +152,7 @@ template <class BusHandlerT, Personality personality, CursorType cursor_type> cl
auto cyles_remaining = cycles.as_integral(); auto cyles_remaining = cycles.as_integral();
while(cyles_remaining--) { while(cyles_remaining--) {
// Check for end of visible characters. // Check for end of visible characters.
if(character_counter_ == registers_[1]) { if(character_counter_ == layout_.horizontal.displayed) {
// TODO: consider skew in character_is_visible_. Or maybe defer until perform_bus_cycle? // TODO: consider skew in character_is_visible_. Or maybe defer until perform_bus_cycle?
character_is_visible_ = false; character_is_visible_ = false;
end_of_line_address_ = bus_state_.refresh_address; end_of_line_address_ = bus_state_.refresh_address;
@@ -146,7 +165,7 @@ template <class BusHandlerT, Personality personality, CursorType cursor_type> cl
bus_state_.refresh_address == (registers_[15] | (registers_[14] << 8)); bus_state_.refresh_address == (registers_[15] | (registers_[14] << 8));
// Check for end-of-line. // Check for end-of-line.
if(character_counter_ == registers_[0]) { if(character_counter_ == layout_.horizontal.total) {
character_counter_ = 0; character_counter_ = 0;
do_end_of_line(); do_end_of_line();
character_is_visible_ = true; character_is_visible_ = true;
@@ -156,7 +175,7 @@ template <class BusHandlerT, Personality personality, CursorType cursor_type> cl
} }
// Check for start of horizontal sync. // Check for start of horizontal sync.
if(character_counter_ == registers_[2]) { if(character_counter_ == layout_.horizontal.start_blank) {
hsync_counter_ = 0; hsync_counter_ = 0;
bus_state_.hsync = true; bus_state_.hsync = true;
} }
@@ -264,7 +283,7 @@ template <class BusHandlerT, Personality personality, CursorType cursor_type> cl
bus_state_.refresh_address = line_address_; bus_state_.refresh_address = line_address_;
character_counter_ = 0; character_counter_ = 0;
character_is_visible_ = (registers_[1] != 0); character_is_visible_ = (layout_.horizontal.displayed != 0);
if constexpr (cursor_type != CursorType::None) { if constexpr (cursor_type != CursorType::None) {
// Check for cursor enable. // Check for cursor enable.
@@ -298,7 +317,15 @@ template <class BusHandlerT, Personality personality, CursorType cursor_type> cl
BusHandlerT &bus_handler_; BusHandlerT &bus_handler_;
BusState bus_state_; BusState bus_state_;
uint8_t registers_[18] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}; struct {
struct {
uint8_t total;
uint8_t displayed;
uint8_t start_blank;
} horizontal;
} layout_;
uint8_t registers_[18]{};
uint8_t dummy_register_ = 0; uint8_t dummy_register_ = 0;
int selected_register_ = 0; int selected_register_ = 0;