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Corrects address loading upon accesses of registers other than 0.

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This commit is contained in:
Thomas Harte 2018-10-10 21:47:48 -04:00
parent 2e379b0834
commit 63fb3f03d1
1 changed files with 7 additions and 4 deletions
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11
Components/9918/9918.cpp
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@ -415,6 +415,10 @@ void TMS9918::set_register(int address, uint8_t value) {
return; return;
} }
// The RAM pointer is always set on a second write, regardless of
// whether the caller is intending to enqueue a VDP operation.
ram_pointer_ = static_cast<uint16_t>(low_write_ | (value << 8));
write_phase_ = false; write_phase_ = false;
if(value & 0x80) { if(value & 0x80) {
switch(personality_) { switch(personality_) {
@ -423,7 +427,6 @@ void TMS9918::set_register(int address, uint8_t value) {
break; break;
case TI::TMS::SMSVDP: case TI::TMS::SMSVDP:
if(value & 0x40) { if(value & 0x40) {
ram_pointer_ = static_cast<uint16_t>(low_write_ | (value << 8));
master_system_.cram_is_selected = true; master_system_.cram_is_selected = true;
return; return;
} }
@ -507,7 +510,6 @@ void TMS9918::set_register(int address, uint8_t value) {
} }
} else { } else {
// This is an access via the RAM pointer. // This is an access via the RAM pointer.
ram_pointer_ = static_cast<uint16_t>(low_write_ | (value << 8));
if(!(value & 0x40)) { if(!(value & 0x40)) {
// A read request is enqueued upon setting the address; conversely a write // A read request is enqueued upon setting the address; conversely a write
// won't be enqueued unless and until some actual data is supplied. // won't be enqueued unless and until some actual data is supplied.
@ -518,8 +520,9 @@ void TMS9918::set_register(int address, uint8_t value) {
} }
uint8_t TMS9918::get_current_line() { uint8_t TMS9918::get_current_line() {
const int source_row = (column_ < mode_timing_.line_interrupt_position) ? (row_ + mode_timing_.pixel_lines - 1)%mode_timing_.pixel_lines : row_; int source_row = (column_ < mode_timing_.line_interrupt_position) ? (row_ + mode_timing_.pixel_lines - 1)%mode_timing_.pixel_lines : row_;
// This assumes NTSC 192-line. TODO: other modes.
if(source_row >= 0xdb) source_row -= 5;
return static_cast<uint8_t>(source_row); return static_cast<uint8_t>(source_row);
} }