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Correct wrapping behaviour for (d, x).

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This commit is contained in:
Thomas Harte 2023-07-28 13:39:21 -04:00
parent e9347168e6
commit 0f1468adfd
1 changed files with 11 additions and 6 deletions
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17
Processors/65816/Implementation/65816Implementation.hpp
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@ -359,15 +359,20 @@ template <typename BusHandler, bool uses_ready_line> void Processor<BusHandler,
continue;
case OperationConstructDirectIndexedIndirect:
data_address_ = (
((registers_.direct + registers_.x.full + instruction_buffer_.value) & registers_.e_masks[1]) +
(registers_.direct & registers_.e_masks[0])
) & 0xffff;
data_address_increment_mask_ = 0x00'ff'ff;
// Emulation mode plus DL = 0 is required for 6502-style functionality where
// only the low byte is the result of the indirect calculation.
if(!(registers_.direct&0xff)) {
data_address_ = (
((registers_.direct + registers_.x.full + instruction_buffer_.value) & registers_.e_masks[1]) +
(registers_.direct & registers_.e_masks[0])
) & 0xffff;
++next_op_;
} else {
data_address_ = (
registers_.direct + registers_.x.full + instruction_buffer_.value
) & 0xffff;
}
data_address_increment_mask_ = 0x00'ff'ff;
continue;
case OperationConstructDirectIndirectIndexedLong: