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Tidies up some of the TMS' magic constants.

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This commit is contained in:
Thomas Harte 2017-12-09 23:08:07 -05:00
parent 042edc72f7
commit b3fbd0f352
2 changed files with 23 additions and 6 deletions
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18
Components/9918/9918.cpp
View File

@ -47,6 +47,12 @@ const uint32_t palette[16] = {
palette_pack(255, 255, 255)
};
const uint8_t StatusInterrupt = 0x80;
const uint8_t StatusFifthSprite = 0x40;
const int StatusSpriteCollisionShift = 5;
const uint8_t StatusSpriteCollision = 0x20;
}
TMS9918::TMS9918(Personality p) :
@ -67,7 +73,7 @@ std::shared_ptr<Outputs::CRT::CRT> TMS9918::get_crt() {
}
void TMS9918::test_sprite(int sprite_number) {
if(!(status_ & 0x40)) {
if(!(status_ & StatusFifthSprite)) {
status_ = static_cast<uint8_t>((status_ & ~31) | sprite_number);
}
if(sprites_stopped_)
@ -85,7 +91,7 @@ void TMS9918::test_sprite(int sprite_number) {
const int active_sprite_slot = sprite_sets_[active_sprite_set_].active_sprite_slot;
if(active_sprite_slot == 4) {
status_ |= 0x40;
status_ |= StatusFifthSprite;
return;
}
@ -416,7 +422,7 @@ void TMS9918::run_for(const HalfCycles cycles) {
} else if(sprite.shift_position < 32) {
int mask = sprite.image[sprite.shift_position >> 4] << ((sprite.shift_position&15) >> 1);
mask = (mask >> 7) & 1;
status_ |= (mask & sprite_mask) << 5;
status_ |= (mask & sprite_mask) << StatusSpriteCollisionShift;
sprite_mask |= mask;
sprite.shift_position += shift_advance;
@ -481,7 +487,7 @@ void TMS9918::run_for(const HalfCycles cycles) {
if(column_ == 342) {
access_pointer_ = column_ = output_column_ = 0;
row_ = (row_ + 1) % frame_lines_;
if(row_ == 192) status_ |= 0x80;
if(row_ == 192) status_ |= StatusInterrupt;
screen_mode_ = next_screen_mode_;
blank_screen_ = next_blank_screen_;
@ -599,7 +605,7 @@ uint8_t TMS9918::get_register(int address) {
// Reads from address 1 get the status register.
uint8_t result = status_;
status_ &= ~(0x80 | 0x40 | 0x20);
status_ &= ~(StatusInterrupt | StatusFifthSprite | StatusSpriteCollision);
return result;
}
@ -613,5 +619,5 @@ uint8_t TMS9918::get_register(int address) {
}
bool TMS9918::get_interrupt_line() {
return (status_ & 0x80) && generate_interrupts_;
return (status_ & StatusInterrupt) && generate_interrupts_;
}

11
Components/9918/9918.hpp
View File

@ -44,7 +44,18 @@ class TMS9918 {
void set_register(int address, uint8_t value);
uint8_t get_register(int address);
/*!
Returns the amount of time until get_interrupt_line would next return true if
there are no interceding calls to set_register or get_register.
If get_interrupt_line is true now, returns zero. If get_interrupt_line would
never return true, returns -1.
*/
HalfCycles get_time_until_interrupt();
/*!
@returns @c true if the interrupt line is currently active; @c false otherwise.
*/
bool get_interrupt_line();
private: