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[patinho] Implement SUS instruction

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This commit is contained in:
Felipe Corrêa da Silva Sanches 2015-11-30 16:46:44 -02:00
parent 9729ebc804
commit cc0ff74b62
1 changed files with 13 additions and 0 deletions
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13
src/devices/cpu/patinhofeio/patinho_feio.cpp
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@ -424,6 +424,19 @@ void patinho_feio_cpu_device::execute_instruction()
if (ACC == 0)
PC = addr;
return;
case 0xE0:
//SUS = "Subtrai um ou Salta": Subtract one from the data in the given address
// or, if the data is zero, then simply skip a couple bytes.
addr = compute_effective_address((opcode & 0x0F) << 8 | READ_BYTE_PATINHO(PC));
INCREMENT_PC_4K;
value = READ_BYTE_PATINHO(addr);
if (value > 0){
WRITE_BYTE_PATINHO(addr, value-1);
} else {
INCREMENT_PC_4K;
INCREMENT_PC_4K;
}
return;
case 0xF0:
//PUG = "Pula e guarda": Jump and store.
// It stores the return address to addr and addr+1