M src/arm.c → src/arm.c

@@ -1,5 +1,38 @@
 #include "arm.h"
 
+static void _ARMSetMode(struct ARMCore*, enum ExecutionMode);
+static ARMInstruction _ARMLoadInstructionARM(struct ARMMemory*, uint32_t address);
+static ARMInstruction _ARMLoadInstructionThumb(struct ARMMemory*, uint32_t address);
+
+static void _ARMSetMode(struct ARMCore* cpu, enum ExecutionMode executionMode) {
+	if (executionMode == cpu->executionMode) {
+		return;
+	}
+
+	cpu->executionMode = executionMode;
+	switch (executionMode) {
+	case MODE_ARM:
+		cpu->cpsr.t = 0;
+		cpu->instructionWidth = WORD_SIZE_ARM;
+		cpu->loadInstruction = _ARMLoadInstructionARM;
+		break;
+	case MODE_THUMB:
+		cpu->cpsr.t = 1;
+		cpu->instructionWidth = WORD_SIZE_THUMB;
+		cpu->loadInstruction = _ARMLoadInstructionThumb;
+	}
+}
+
+static ARMInstruction _ARMLoadInstructionARM(struct ARMMemory* memory, uint32_t address) {
+	int32_t opcode = memory->load32(memory, address);
+	return 0;
+}
+
+static ARMInstruction _ARMLoadInstructionThumb(struct ARMMemory* memory, uint32_t address) {
+	uint16_t opcode = memory->loadU16(memory, address);
+	return 0;
+}
+
 void ARMInit(struct ARMCore* cpu) {
 	int i;
 	for (i = 0; i < 16; ++i) {
@@ -16,8 +49,16 @@ cpu->shifterCarryOut = 0;
 
 	cpu->memory = 0;
 	cpu->board = 0;
+
+	cpu->executionMode = MODE_THUMB;
+	_ARMSetMode(cpu, MODE_ARM);
+}
+
+void ARMAssociateMemory(struct ARMCore* cpu, struct ARMMemory* memory) {
+	cpu->memory = memory;
 }
 
 void ARMCycle(struct ARMCore* cpu) {
 	// TODO
+	ARMInstruction instruction = cpu->loadInstruction(cpu->memory, cpu->gprs[ARM_PC] - cpu->instructionWidth);
 }

M src/arm.h → src/arm.h

@@ -24,6 +24,11 @@ MODE_UNDEFINED = 0x1B,
 	MODE_SYSTEM = 0x1F
 };
 
+enum WordSize {
+	WORD_SIZE_ARM = 4,
+	WORD_SIZE_THUMB = 2
+};
+
 enum ExecutionVector {
 	BASE_RESET = 0x00000000,
 	BASE_UNDEF = 0x00000004,
@@ -34,6 +39,9 @@ BASE_IRQ = 0x00000018,
 	BASE_FIQ = 0x0000001C
 };
 
+struct ARMCore;
+typedef void (*ARMInstruction)(struct ARMCore*);
+
 union PSR {
 	struct {
 		int exec : 4;
@@ -51,7 +59,14 @@
 	int32_t packed;
 };
 
-struct ARMMemory;
+struct ARMMemory {
+	int32_t (*load32)(struct ARMMemory*, uint32_t address);
+	int16_t (*load16)(struct ARMMemory*, uint32_t address);
+	uint16_t (*loadU16)(struct ARMMemory*, uint32_t address);
+	int8_t (*load8)(struct ARMMemory*, uint32_t address);
+	uint8_t (*loadU8)(struct ARMMemory*, uint32_t address);
+};
+
 struct ARMBoard;
 
 struct ARMCore {
@@ -64,11 +79,18 @@
 	int32_t shifterOperand;
 	int32_t shifterCarryOut;
 
+	int instructionWidth;
+
+	ARMInstruction (*loadInstruction)(struct ARMMemory*, uint32_t address);
+	enum ExecutionMode executionMode;
+
 	struct ARMMemory* memory;
 	struct ARMBoard* board;
 };
 
 void ARMInit(struct ARMCore* cpu);
+void ARMAssociateMemory(struct ARMCore* cpu, struct ARMMemory* memory);
+
 void ARMCycle(struct ARMCore* cpu);
 
 #endif