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Implements screen 2 addressing.

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This commit is contained in:
Thomas Harte 2017-12-02 14:05:52 -05:00
parent 3c8d2d579d
commit d3dd8f3f2a
1 changed files with 14 additions and 4 deletions
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18
Components/9918/9918.cpp
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@ -131,8 +131,18 @@ void TMS9918::run_for(const HalfCycles cycles) {
if(access_pointer_ >= 26) {
int end = std::min(154, access_slot);
int row_base = pattern_name_address_;
int pattern_base = pattern_generator_table_address_;
int colour_base = colour_table_address_;
int colour_shift = 3;
if(screen_mode_ == 1) {
pattern_base &= 0x2000 | ((row_ & 0xc0) << 5);
colour_base &= 0x2000 | ((row_ & 0xc0) << 5);
colour_shift = 0;
}
row_base += (row_ << 2)&~31;
// TODO: optimise this mess.
const int row_base = pattern_name_address_ + ((row_ << 2)&~31);
while(access_pointer_ < end) {
int character_column = ((access_pointer_ - 26) >> 2);
switch(access_pointer_&3) {
@ -141,10 +151,10 @@ void TMS9918::run_for(const HalfCycles cycles) {
break;
case 1: break; // TODO: sprites / CPU access.
case 2:
colour_buffer_[character_column] = ram_[colour_table_address_ + (pattern_name_ >> 3)];
colour_buffer_[character_column] = ram_[colour_base + (pattern_name_ >> colour_shift)];
break;
case 3:
pattern_buffer_[character_column] = ram_[pattern_generator_table_address_ + (pattern_name_ << 3) + (row_ & 7)];
pattern_buffer_[character_column] = ram_[pattern_base + (pattern_name_ << 3) + (row_ & 7)];
break;
}
access_pointer_++;
@ -318,7 +328,7 @@ void TMS9918::set_register(int address, uint8_t value) {
case 1:
next_blank_screen_ = !(low_write_ & 0x40);
generate_interrupts_ = !!(low_write_ & 0x20);
next_screen_mode_ = (screen_mode_ & 1) | ((low_write_ & 0x18) >> 3);
next_screen_mode_ = (next_screen_mode_ & 1) | ((low_write_ & 0x18) >> 3);
sprites_16x16_ = !!(low_write_ & 0x02);
sprites_magnified_ = !!(low_write_ & 0x01);
printf("NSM: %02x\n", next_screen_mode_);