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Introduces horizontal counter latching and reading.

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Then makes a new guess at frame IRQ position. But gets it wrong. Hmmm.
This commit is contained in:
Thomas Harte
2018-10-11 19:56:32 -04:00
parent 9a933993f5
commit 52e02db5c8
4 changed files with 61 additions and 10 deletions
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Components/9918/9918.cpp
+17 -1
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@@ -526,8 +526,9 @@ uint8_t TMS9918::get_current_line() {
int source_row = (column_ < mode_timing_.line_interrupt_position) ? (row_ + mode_timing_.total_lines - 1)%mode_timing_.total_lines : row_;
// This assumes NTSC 192-line. TODO: other modes.
if(source_row >= 0xdb) source_row -= 6;
// printf("Current row: %d -> %d\n", row_, source_row);
return static_cast<uint8_t>(source_row);
}
/*
TODO: Full proper sequence of current lines:
@@ -539,6 +540,21 @@ uint8_t TMS9918::get_current_line() {
PAL 256x224 00-FF, 00-02, CA-FF
PAL 256x240 00-FF, 00-0A, D2-FF
*/
}
uint8_t TMS9918::get_latched_horizontal_counter() {
// Translate from internal numbering, which puts pixel output
// in the final 256 pixels of 342, to the public numbering,
// which makes the 256 pixels the first 256 spots, but starts
// counting at -48, and returns only the top 8 bits of the number.
int public_counter = latched_column_ - 86;
if(public_counter < -48) public_counter += 342;
return uint8_t(public_counter >> 1);
}
void TMS9918::latch_horizontal_counter() {
latched_column_ = column_;
}
uint8_t TMS9918::get_register(int address) {
write_phase_ = false;