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Relocate Yamaha line interrupt.

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This commit is contained in:
Thomas Harte 2023-05-16 13:01:23 -04:00
parent 747dc09a80
commit 3014c957e7
4 changed files with 44 additions and 14 deletions
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51
Components/9918/Implementation/9918.cpp
View File

@ -44,11 +44,10 @@ Base<personality>::Base() :
}
if constexpr (is_yamaha_vdp(personality)) {
// TODO: start of sync, or end of sync? Or elsewhere.
// Note that there's a bug elsewhere if the proper value of this is zero in the
// "if started before but reached this count" logic — that is boxed into considering
// a single line only so never sees starts before 0.
mode_timing_.line_interrupt_position = LineLayout<personality>::EndOfSync;
// TODO: this is used for interrupt _prediction_ but won't handle text modes correctly, and indeed
// can't be just a single value where the programmer has changed into or out of text modes during the
// middle of a line, since screen mode is latched (so it'll be one value for that line, another from then onwards).a
mode_timing_.line_interrupt_position = LineLayout<personality>::EndOfPixels;
}
// Establish that output is delayed after reading by `output_lag` cycles,
@ -275,11 +274,14 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
// -------------------------------
// Check for interrupt conditions.
// -------------------------------
if(this->fetch_pointer_.column < this->mode_timing_.line_interrupt_position && end_column >= this->mode_timing_.line_interrupt_position) {
if constexpr (is_sega_vdp(personality)) {
// The Sega VDP offers a decrementing counter for triggering line interrupts;
// it is reloaded either when it overflows or upon every non-pixel line after the first.
// It is otherwise decremented.
if constexpr (is_sega_vdp(personality)) {
if(
this->fetch_pointer_.column < this->mode_timing_.line_interrupt_position &&
end_column >= this->mode_timing_.line_interrupt_position
) {
if(this->fetch_pointer_.row >= 0 && this->fetch_pointer_.row <= this->mode_timing_.pixel_lines) {
if(!this->line_interrupt_counter_) {
this->line_interrupt_pending_ = true;
@ -291,14 +293,27 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
this->line_interrupt_counter_ = this->line_interrupt_target_;
}
}
}
if constexpr (is_yamaha_vdp(personality)) {
if(
this->vertical_active_ &&
this->fetch_pointer_.row == ((this->line_interrupt_target_ - Storage<personality>::vertical_offset_) & 0xff)
) {
this->line_interrupt_pending_ = true;
}
if constexpr (is_yamaha_vdp(personality)) {
// The Yamaha VDPs allow the user to specify which line an interrupt should occur on,
// which is relative to the current vertical base. Such an interrupt will occur immediately
// after pixels have ended.
if(
this->vertical_active_ &&
this->fetch_pointer_.column < Storage<personality>::mode_description_.end_cycle &&
end_column >= Storage<personality>::mode_description_.end_cycle &&
this->fetch_pointer_.row == ((this->line_interrupt_target_ - Storage<personality>::vertical_offset_) & 0xff)
) {
this->line_interrupt_pending_ = true;
Storage<personality>::line_matches_ = true;
}
if(
this->fetch_pointer_.column < Storage<personality>::mode_description_.start_cycle &&
end_column >= Storage<personality>::mode_description_.start_cycle
) {
Storage<personality>::line_matches_ = false;
}
}
@ -369,6 +384,13 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
desc.pixels_per_byte = pixels_per_byte(this->underlying_mode_);
desc.width = width(this->underlying_mode_);
desc.rotate_address = interleaves_banks(this->underlying_mode_);
if(is_text(this->underlying_mode_)) {
desc.start_cycle = LineLayout<personality>::TextModeEndOfLeftBorder;
desc.end_cycle = LineLayout<personality>::TextModeEndOfPixels;
} else {
desc.start_cycle = LineLayout<personality>::EndOfLeftBorder;
desc.end_cycle = LineLayout<personality>::EndOfPixels;
}
}
// Based on the output mode, pick a line mode.
@ -1256,6 +1278,7 @@ HalfCycles TMS9918<personality>::get_next_sequence_point() const {
// Calculate when the next line interrupt will occur.
int next_line_interrupt_row = -1;
int line_interrupt_position = this->mode_timing_.line_interrupt_position;
int cycles_to_next_interrupt_threshold = this->mode_timing_.line_interrupt_position - this->fetch_pointer_.column;
int line_of_next_interrupt_threshold = this->fetch_pointer_.row;

4
Components/9918/Implementation/AccessEnums.hpp
View File

@ -78,6 +78,10 @@ constexpr bool interleaves_banks(ScreenMode mode) {
return mode == ScreenMode::YamahaGraphics6 || mode == ScreenMode::YamahaGraphics7;
}
constexpr bool is_text(ScreenMode mode) {
return mode == ScreenMode::Text || mode == ScreenMode::YamahaText80;
}
enum class FetchMode {
Text,
Character,

1
Components/9918/Implementation/Storage.hpp
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@ -402,6 +402,7 @@ template <Personality personality> struct Storage<personality, std::enable_if_t<
uint8_t colour_status_ = 0;
uint16_t colour_location_ = 0;
uint16_t collision_location_[2]{};
bool line_matches_ = false;
Storage() noexcept {
// Seed to something valid.

2
Components/9918/Implementation/YamahaCommands.hpp
View File

@ -89,6 +89,8 @@ struct ModeDescription {
int width = 256;
int pixels_per_byte = 4;
bool rotate_address = false;
int start_cycle = 0;
int end_cycle = 0;
};
struct Command {