cpu/cpu - Treat a call to an ISR as a step
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2 changed files with 12 additions and 4 deletions
14
cpu/cpu.cpp
14
cpu/cpu.cpp
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@ -1,4 +1,5 @@
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#include "cpu.h"
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#include "panic.h"
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void Cpu_state::setAF(u16 v)
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{
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@ -26,8 +27,10 @@ Cpu::Cpu(Mem_device* bus)
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void Cpu::step()
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{
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handleInterrupts();
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executeInstruction();
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if(!handleInterrupts()) // if no isr has been called, decode an instruction
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{
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executeInstruction();
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}
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}
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void Cpu::reset()
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@ -185,7 +188,7 @@ void Cpu::aluop8(AluOp op, u8 lhs, u8 rhs, u8& out, bool update_carry)
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out = res;
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}
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void Cpu::handleInterrupts()
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bool Cpu::handleInterrupts()
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{
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// servicable interrupts (assuming IME is on)
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u8 si = state.IE & state.IF & INT_MASK;
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@ -202,11 +205,16 @@ void Cpu::handleInterrupts()
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else if (si & INT_Timer) { it = INT_Timer; isr = 0x50; }
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else if (si & INT_Serial) { it = INT_Serial; isr = 0x58; }
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else if (si & INT_Joypad) { it = INT_Joypad; isr = 0x60; }
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else panic("Can't find pending interrupt IE=%02x IF=%02x\n", state.IE, state.IF);
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state.IME = IME_OFF; // Disable IME
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state.IF &= ~it; // clear interrupt in IF
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doCall(isr); // Call interrupt service routine
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processed_mcycles += 5;
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return true;
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}
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return false;
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}
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@ -119,7 +119,7 @@ private:
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bool decodeCond(u8 cc);
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void handleInterrupts();
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bool handleInterrupts();
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void executeInstruction();
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void reset();
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