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system size registers fix

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folkert van heusden 2022-03-21 19:22:40 +01:00
parent 08427e7db9
commit 8b361fad4a
1 changed files with 8 additions and 2 deletions
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10
bus.cpp
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@ -237,8 +237,14 @@ uint16_t bus::read(const uint16_t a, const bool word_mode, const bool use_prev)
D(fprintf(stderr, "bus::readWord: odd address UNHANDLED %o\n", a);)
D(fprintf(stderr, "UNHANDLED read %o(%c)\n", a, word_mode ? 'B' : ' ');)
if (a == 0177760)
return std::min(n_pages * 8192, 65536) - 4096;
// LO size register field must be all 1s, so subtract 1
constexpr const uint32_t system_size = n_pages * 8192 - 4096 - 1;
if (a == 0177762) // system size HI
return system_size >> 16;
if (a == 0177760) // system size LO
return system_size & 65535;
// c -> busError();