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Clean up some dangling timing changes.

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This commit is contained in:
Thomas Harte 2023-04-25 23:16:21 -04:00
parent 8cd38094fc
commit b5d9586362
2 changed files with 13 additions and 11 deletions
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20
Components/9918/Implementation/9918.cpp
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@ -31,11 +31,15 @@ Base<personality>::Base() :
// into whether there's a more natural form. It feels unlikely given the diversity of chips modelled. // into whether there's a more natural form. It feels unlikely given the diversity of chips modelled.
if constexpr (is_sega_vdp(personality)) { if constexpr (is_sega_vdp(personality)) {
// TODO: all these relate to the old line timing; resource and review. // Cf. https://www.smspower.org/forums/8161-SMSDisplayTiming
mode_timing_.line_interrupt_position = 64; // "For a line interrupt, /INT is pulled low 608 mclks into the appropriate scanline relative to pixel 0.
// This is 3 mclks before the rising edge of /HSYNC which starts the next scanline."
mode_timing_.line_interrupt_position = (LineLayout<personality>::EndOfLeftBorder + 304) % Timing<personality>::CyclesPerLine;
mode_timing_.end_of_frame_interrupt_position.column = 63; // For a frame interrupt, /INT is pulled low 607 mclks into scanline 192 (of scanlines 0 through 261) relative to pixel 0.
// This is 4 mclks before the rising edge of /HSYNC which starts the next scanline.
mode_timing_.end_of_frame_interrupt_position.column = mode_timing_.line_interrupt_position - 1;
mode_timing_.end_of_frame_interrupt_position.row = 193; mode_timing_.end_of_frame_interrupt_position.row = 193;
} }
@ -46,11 +50,7 @@ Base<personality>::Base() :
// Establish that output is delayed after reading by `output_lag` cycles, // Establish that output is delayed after reading by `output_lag` cycles,
// i.e. the fetch pointer is currently _ahead_ of the output pointer. // i.e. the fetch pointer is currently _ahead_ of the output pointer.
//
// TODO: Start at a random position.
output_pointer_.row = output_pointer_.column = 0; output_pointer_.row = output_pointer_.column = 0;
// output_pointer_.row = rand() % 262;
// output_pointer_.column = rand() % (Timing<personality>::CyclesPerLine - output_lag);
fetch_pointer_ = output_pointer_; fetch_pointer_ = output_pointer_;
fetch_pointer_.column += output_lag; fetch_pointer_.column += output_lag;
@ -1180,7 +1180,7 @@ uint8_t TMS9918<personality>::read(int address) {
template <Personality personality> template <Personality personality>
int Base<personality>::fetch_line() const { int Base<personality>::fetch_line() const {
// This is the proper Master System value; TODO: what's correct for Yamaha, etc? // This is the proper Master System value; TODO: what's correct for Yamaha, etc?
constexpr int row_change_position = 63; constexpr int row_change_position = 31;
return return
(this->fetch_pointer_.column < row_change_position) (this->fetch_pointer_.column < row_change_position)
@ -1320,7 +1320,7 @@ bool TMS9918<personality>::get_interrupt_line() const {
(this->enable_line_interrupts_ && this->line_interrupt_pending_); (this->enable_line_interrupts_ && this->line_interrupt_pending_);
} }
// TODO: [potentially] remove Master System timing assumptions in latch and get_latched below. // TODO: [potentially] remove Master System timing assumptions in latch and get_latched below, if any other VDP uses these calls.
template <Personality personality>uint8_t TMS9918<personality>::get_latched_horizontal_counter() const { template <Personality personality>uint8_t TMS9918<personality>::get_latched_horizontal_counter() const {
// Translate from internal numbering, which puts pixel output // Translate from internal numbering, which puts pixel output
// in the final 256 pixels of 342, to the public numbering, // in the final 256 pixels of 342, to the public numbering,
@ -1329,6 +1329,8 @@ template <Personality personality>uint8_t TMS9918<personality>::get_latched_hori
int public_counter = this->latched_column_ - (342 - 256); int public_counter = this->latched_column_ - (342 - 256);
if(public_counter < -46) public_counter += 342; if(public_counter < -46) public_counter += 342;
return uint8_t(public_counter >> 1); return uint8_t(public_counter >> 1);
// TODO: above is no longer correct.
} }
template <Personality personality> template <Personality personality>

4
Components/9918/Implementation/9918Base.hpp
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@ -173,8 +173,8 @@ template <Personality personality> struct Base: public Storage<personality> {
// Set the position, in cycles, of the two interrupts, // Set the position, in cycles, of the two interrupts,
// within a line. // within a line.
struct { struct {
int column = 4; int column = 313;
int row = 193; int row = 192;
} end_of_frame_interrupt_position; } end_of_frame_interrupt_position;
int line_interrupt_position = -1; int line_interrupt_position = -1;