jake/SplitBit-Emulator
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Added new instructions.

Browse Source 
Added CCF - Clear Carry Flag
Added BRC - Branch on Carry Flag
Improved CALL and RET - All registers but status now saved and restored.
This commit is contained in:
Anachronaut
2024-10-29 21:04:03 -04:00
committed by GitHub
parent f9308338c4
commit a58fb3d694
8 changed files with 255 additions and 112 deletions
Download Patch File Download Diff File Expand all files Collapse all files
Source/Emulator/cpu.c
+50 -8
View File
@@ -121,16 +121,55 @@ uint8_t executeOperation(uint8_t Instruction, CPURegisters *cpu) {
cpu->StackPointer--;
cpu->Data[cpu->StackPointer] = (cpu->ProgramCounter >> 8) & 0xFF;
cpu->StackPointer--;
// Push the Data Pointer to the Stack.
// Order, low byte, high byte
cpu->Data[cpu->StackPointer] = cpu->DataPointer & 0xFF;
cpu->StackPointer--;
cpu->Data[cpu->StackPointer] = (cpu->DataPointer >> 8) & 0xFF;
cpu->StackPointer--;
// Push Q to the Stack.
cpu->Data[cpu->StackPointer] = cpu->Q;
cpu->StackPointer--;
// Push B to the Stack.
cpu->Data[cpu->StackPointer] = cpu->B;
cpu->StackPointer--;
// Push A to the Stack.
cpu->Data[cpu->StackPointer] = cpu->A;
cpu->StackPointer--;
// Perform a Generic Branch to the Address.
genericBranch(cpu);
break;
case 0x15:
// RET - Return from subroutine, restore the Program Counter from the Stack.
// POPP - Pop Data to the Program Counter
// RET - Return from subroutine, restore the registers and set the Program Counter to the Return Address.
// Pop A from the Stack.
cpu->StackPointer++;
cpu->A = cpu->Data[cpu->StackPointer];
// Pop B from the Stack.
cpu->StackPointer++;
cpu->B = cpu->Data[cpu->StackPointer];
// Pop Q from the Stack.
cpu->StackPointer++;
cpu->Q = cpu->Data[cpu->StackPointer];
// Pop the Data Pointer from the Stack.
cpu->StackPointer++;
cpu->DataPointer = (uint16_t)cpu->Data[cpu->StackPointer] << 8;
cpu->StackPointer++;
cpu->DataPointer |= (uint16_t)cpu->Data[cpu->StackPointer];
// Pop the Return Address from the Stack.
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.
// Add 2 to the Program Counter to skip over the address when it returns.
cpu->ProgramCounter += 2;
break;
case 0x16:
// BRC - Do an immediate branch is the Carry Flag is set.
if (cpu->Status & 0x01) {
genericBranch(cpu);
} else {
cpu->ProgramCounter+=2;
}
break;
//
// 2x - Register Operations:
@@ -177,6 +216,10 @@ uint8_t executeOperation(uint8_t Instruction, CPURegisters *cpu) {
cpu->ProgramCounter++;
cpu->B = cpu->Program[cpu->ProgramCounter];
break;
case 0x2F:
// CCF - Clear the Carry Flag.
cpu->Status &= ~0x01;
break;
//
// 3x - Stack Operations:
//
@@ -195,9 +238,8 @@ uint8_t executeOperation(uint8_t Instruction, CPURegisters *cpu) {
cpu->Data[cpu->StackPointer] = cpu->B;
cpu->StackPointer--;
break;
break;
case 0x33:
// PSHD - Push the Data Pointer to the Stack.
// PSHD - Push the Data Pointer Address to the Stack.
// Order, low byte, high byte
cpu->Data[cpu->StackPointer] = cpu->DataPointer & 0xFF;
cpu->StackPointer--;
@@ -205,18 +247,18 @@ uint8_t executeOperation(uint8_t Instruction, CPURegisters *cpu) {
cpu->StackPointer--;
break;
case 0x34:
// POPA - Pop Data to A.
// POPA - Pop A from the Stack.
cpu->StackPointer++;
cpu->A = cpu->Data[cpu->StackPointer];
break;
case 0x35:
// POPB - Pop Data to B.
// POPB - Pop B from the Stack.
cpu->StackPointer++;
cpu->B = cpu->Data[cpu->StackPointer];
break;
case 0x36:
// POPD - Pop Data to the Data Pointer
// POPD - Pop Data Address from the Stack.
cpu->StackPointer++;
cpu->DataPointer = (uint16_t)cpu->Data[cpu->StackPointer] << 8;
cpu->StackPointer++;