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Fix MOVS Instruction #18

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Merged
lmSeryi merged 1 commit into from
Feb 9, 2026
Merged

Fix MOVS Instruction #18

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5 changes: 3 additions & 2 deletions src/RP2040.Core/Cpu/Instructions/BitOps.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -185,10 +185,11 @@ public static void MovRegister(ushort opcode, CortexM0Plus cpu)
public static void Movs(ushort opcode, CortexM0Plus cpu)
{
var value = (uint)(opcode & 0xFF);
var rd = (opcode >> 8) & 7;

cpu.Registers[(opcode >> 8) & 7] = value;
cpu.Registers[rd] = value;

cpu.Registers.N = false;
cpu.Registers.N = (int)value < 0;
cpu.Registers.Z = value == 0;
}

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64 changes: 64 additions & 0 deletions tests/RP2040.Core.Tests/Cpu/Instructions/BitOpsTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -351,6 +351,70 @@ public void Should_LoadImmediateValue_And_UpdateFlags()
Cpu.Registers[R5].Should().Be(128);
Cpu.Registers.PC.Should().Be(0x20000002);
}

[Fact]
public void Should_ClearLowerTwoBits_When_WritingToStackPointer()
{
// Arrange
var opcode = InstructionEmiter.Mov(SP, R5);
Bus.WriteHalfWord(0x20000000, opcode);

Cpu.Registers[R5] = 0x53;

// Act
Cpu.Step();

// Assert
Cpu.Registers.SP.Should().Be(0x50);
}

[Fact]
public void Should_ClearLeastSignificantBit_When_WritingToProgramCounter()
{
// Arrange
var opcode = InstructionEmiter.Mov(PC, R5);
Bus.WriteHalfWord(0x20000000, opcode);

Cpu.Registers[R5] = 0x53;

// Act
Cpu.Step();

// Assert
Cpu.Registers.PC.Should().Be(0x52);
}

[Fact]
public void Should_CopyValue_BetweenRegisters()
{
// Arrange
var opcode = InstructionEmiter.Mov(R6, R5);
Bus.WriteHalfWord(0x20000000, opcode);

Cpu.Registers[R5] = 50;

// Act
Cpu.Step();

// Assert
Cpu.Registers[R6].Should().Be(50);
}

[Fact]
public void Should_CopyNegativeValue_BetweenRegisters()
{
// Arrange
var opcode = InstructionEmiter.Mov(R6, R5);
Bus.WriteHalfWord(0x20000000, opcode);

Cpu.Registers[R5] = unchecked((uint)-50);

// Act
Cpu.Step();

// Assert
Cpu.Registers[R6].Should().Be(unchecked((uint)-50));
}
}

public class Mvns : CpuTestBase
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