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Fix Apple II/II+/IIe hbl row < 64 read addresses

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See #1180
This commit is contained in:
Ryan Schmidt 2023-10-23 05:18:13 -05:00
parent 577b01e80b
commit c272632b5a
1 changed files with 13 additions and 1 deletions
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14
Machines/Apple/AppleII/Video.hpp
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@ -150,6 +150,9 @@ template <class BusHandler, bool is_iie> class Video: public VideoBase {
mapped_row %= 262;
mapped_column %= 65;
// Remember if we're in a horizontal blanking interval.
int hbl = mapped_column < 25;
// Vertical blanking rows read eight bytes earlier.
if(mapped_row >= 192) {
mapped_column -= 8;
@ -162,8 +165,17 @@ template <class BusHandler, bool is_iie> class Video: public VideoBase {
mapped_row %= 192;
}
// Calculate the address and return the value.
// Calculate the address.
uint16_t read_address = uint16_t(get_row_address(mapped_row) + mapped_column - 25);
if(hbl) {
// Wraparound addressing within 128 byte sections.
if(mapped_row < 64) {
read_address += 128;
}
}
// Read the address and return the value.
uint8_t value, aux_value;
bus_handler_.perform_read(read_address, 1, &value, &aux_value);
return value;