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Merge pull request #1252 from TomHarte/CGAAddresses

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Revise guess as to CGA address wrapping.
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Thomas Harte 2023-12-06 22:32:54 -05:00 committed by GitHub
commit d696c15be5
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1 changed files with 5 additions and 3 deletions
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8
Machines/PCCompatible/CGA.hpp
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@ -263,7 +263,9 @@ class CGA {
// character code + attributes except that these are two bytes worth of graphics.
//
// Meanwhile, row address is used to invent a 15th address line.
const auto base_address = ((state.refresh_address << 1) + (state.row_address << 13)) & 0x3fff;
const auto base_address =
((state.refresh_address & 0xfff) << 1) +
((state.row_address & 1) << 13);
const uint8_t bitmap[] = {
ram[base_address],
ram[base_address + 1],
@ -299,8 +301,8 @@ class CGA {
}
void serialise_text(const Motorola::CRTC::BusState &state) {
const uint8_t attributes = ram[((state.refresh_address << 1) + 1) & 0xfff];
const uint8_t glyph = ram[((state.refresh_address << 1) + 0) & 0xfff];
const uint8_t attributes = ram[((state.refresh_address << 1) + 1) & 0x3fff];
const uint8_t glyph = ram[((state.refresh_address << 1) + 0) & 0x3fff];
const uint8_t row = font[(glyph * 8) + state.row_address];
uint8_t colours[2] = {