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CALL and RET instructions.

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Changed PSHP and POPP into CALL and RET, streamlining their use for subroutine calls.
Updated Assembler and Emulator.
New demonstration programs.
This commit is contained in:
Anachronaut
2024-10-27 19:18:54 -04:00
committed by GitHub
parent 78f827e9dc
commit 992e44ca12
7 changed files with 152 additions and 54 deletions
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Source/Emulator/cpu.c
+22 -19
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@@ -114,6 +114,24 @@ uint8_t executeOperation(uint8_t Instruction, CPURegisters *cpu) {
cpu->ProgramCounter+=2;
}
break;
case 0x14:
// CALL - Push the Program Counter to the Stack, and perform an immediate branch.
// Order, low byte, high byte
cpu->Data[cpu->StackPointer] = cpu->ProgramCounter & 0xFF;
cpu->StackPointer--;
cpu->Data[cpu->StackPointer] = (cpu->ProgramCounter >> 8) & 0xFF;
cpu->StackPointer--;
genericBranch(cpu);
break;
case 0x15:
// RET - Return from subroutine, restore the Program Counter from the Stack.
// POPP - Pop Data to the Program Counter
cpu->StackPointer++;
cpu->ProgramCounter = (uint16_t)cpu->Data[cpu->StackPointer] << 8;
cpu->StackPointer++;
cpu->ProgramCounter = cpu->ProgramCounter | (uint16_t)cpu->Data[cpu->StackPointer];
cpu->ProgramCounter += 2; // Because it needs to skip over the address when it returns.
break;
//
// 2x - Register Operations:
//
@@ -177,15 +195,8 @@ uint8_t executeOperation(uint8_t Instruction, CPURegisters *cpu) {
cpu->Data[cpu->StackPointer] = cpu->B;
cpu->StackPointer--;
break;
case 0x33:
// PSHP - Push the Program Counter to the Stack.
// Order, low byte, high byte
cpu->Data[cpu->StackPointer] = cpu->ProgramCounter & 0xFF;
cpu->StackPointer--;
cpu->Data[cpu->StackPointer] = (cpu->ProgramCounter >> 8) & 0xFF;
cpu->StackPointer--;
break;
case 0x34:
case 0x33:
// PSHD - Push the Data Pointer to the Stack.
// Order, low byte, high byte
cpu->Data[cpu->StackPointer] = cpu->DataPointer & 0xFF;
@@ -193,26 +204,18 @@ uint8_t executeOperation(uint8_t Instruction, CPURegisters *cpu) {
cpu->Data[cpu->StackPointer] = (cpu->DataPointer >> 8) & 0xFF;
cpu->StackPointer--;
break;
case 0x35:
case 0x34:
// POPA - Pop Data to A.
cpu->StackPointer++;
cpu->A = cpu->Data[cpu->StackPointer];
break;
case 0x36:
case 0x35:
// POPB - Pop Data to B.
cpu->StackPointer++;
cpu->B = cpu->Data[cpu->StackPointer];
break;
case 0x37:
// POPP - Pop Data to the Program Counter
cpu->StackPointer++;
cpu->ProgramCounter = (uint16_t)cpu->Data[cpu->StackPointer] << 8;
cpu->StackPointer++;
cpu->ProgramCounter = cpu->ProgramCounter | (uint16_t)cpu->Data[cpu->StackPointer];
cpu->ProgramCounter += 3; // Because it needs to skip over the subsequent branch instruction on return.
break;
case 0x38:
case 0x36:
// POPD - Pop Data to the Data Pointer
cpu->StackPointer++;
cpu->DataPointer = (uint16_t)cpu->Data[cpu->StackPointer] << 8;