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Fixes a couple of interrupt prediction errors.

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This commit is contained in:
Thomas Harte 2018-10-20 18:25:28 -04:00
parent b61de65b43
commit 30b99f0049
1 changed files with 3 additions and 3 deletions
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6
Components/9918/9918.cpp
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@ -629,7 +629,7 @@ uint8_t TMS9918::get_register(int address) {
}
HalfCycles Base::half_cycles_before_internal_cycles(int internal_cycles) {
return HalfCycles(((internal_cycles << 2) - cycles_error_) / 3);
return HalfCycles(((internal_cycles << 2) + (2 - cycles_error_)) / 3);
}
HalfCycles TMS9918::get_time_until_interrupt() {
@ -646,7 +646,7 @@ HalfCycles TMS9918::get_time_until_interrupt() {
if(!enable_line_interrupts_) return half_cycles_before_internal_cycles(time_until_frame_interrupt);
// Calculate the row upon which the next line interrupt will occur;
// Calculate the row upon which the next line interrupt will occur.
int next_line_interrupt_row = -1;
if(is_sega_vdp(personality_)) {
@ -675,7 +675,7 @@ HalfCycles TMS9918::get_time_until_interrupt() {
if(!local_cycles_until_next_tick) local_cycles_until_next_tick += 342;
const int local_cycles_until_line_interrupt = local_cycles_until_next_tick + (next_line_interrupt_row - write_pointer_.row) * 342;
if(!generate_interrupts_) return half_cycles_before_internal_cycles(time_until_frame_interrupt);
if(!generate_interrupts_) return half_cycles_before_internal_cycles(local_cycles_until_line_interrupt);
// Return whichever interrupt is closer.
return half_cycles_before_internal_cycles(std::min(local_cycles_until_line_interrupt, time_until_frame_interrupt));