Initial cpu and instruction parsing

include/cart.h

@@ -21,4 +21,7 @@ typedef struct {
 
 bool cart_load(char *cart);
 
-rom_header *get_rom_header();
+rom_header *get_rom_header();
+
+u8 cart_read(u16 address);
+void cart_write(u16 address, u8 value);

include/common.h

@@ -14,4 +14,6 @@ typedef uint64_t u64;
 #define BIT_SET(a, n, on) (on ? (a) |= (1 << n) : (a) &= !(1 << n))
 #define BETWEEN(a, b, c) ((a >= b) && (a <= c))
 
-void delay(u32 ms);
+void delay(u32 ms);
+
+#define NO_IMPL { fprintf(stderr, "NOT YET IMPLEMENTED\n"); exit(-5); }

include/cpu.h

@@ -1,6 +1,34 @@
 #pragma once
 
 #include <common.h>
+#include <instructions.h>
+
+typedef struct {
+    u8 a;
+    u8 f;
+    u8 b;
+    u8 c;
+    u8 d;
+    u8 e;
+    u8 h;
+    u8 l;
+    u16 pc;
+    u16 sp;
+} cpu_registers;
+
+typedef struct {
+    cpu_registers regs;
+
+    //current fetch...
+    u16 fetched_data;
+    u16 mem_dest;
+    bool dest_is_mem;
+    u8 cur_opcode;
+    instruction *cur_inst;
+
+    bool halted;
+    bool stepping;
+} cpu_context;
 
 void cpu_init();
 bool cpu_step();

include/emu.h

@@ -9,4 +9,6 @@ typedef struct {
 } emu_context;
 
 int emu_run(int, char**);
-emu_context *emu_get_context();
+emu_context *emu_get_context();
+
+void emu_cycles(int cpu_cycles);

include/instructions.h

@@ -0,0 +1,111 @@
+#pragma once
+#include <common.h>
+
+typedef enum {
+    AM_R_D16,
+    AM_R_R,
+    AM_MR_R,
+    AM_R,
+    AM_R_D8,
+    AM_R_MR,
+    AM_R_HLI,
+    AM_R_HLD,
+    AM_HLI_R,
+    AM_HLD_R,
+    AM_R_A8,
+    AM_A8_R,
+    AM_HL_SPR,
+    AM_D16,
+    AM_D8,
+    AM_IMP,
+    AM_D16_R,
+    AM_MR_D8,
+    AM_MR,
+    AM_A16_R,
+    AM_R_A16
+} addr_mode;
+
+typedef enum {
+    RT_NONE,
+    RT_A,
+    RT_F,
+    RT_B,
+    RT_C,
+    RT_D,
+    RT_E,
+    RT_H,
+    RT_L,
+    RT_AF,
+    RT_BC,
+    RT_DE,
+    RT_HL,
+    RT_SP,
+    RT_PC
+} reg_type;
+
+typedef enum {
+    IN_NONE,
+    IN_NOP,
+    IN_LD,
+    IN_INC,
+    IN_DEC,
+    IN_RLCA,
+    IN_ADD,
+    IN_RRCA,
+    IN_STOP,
+    IN_RLA,
+    IN_JR,
+    IN_RRA,
+    IN_DAA,
+    IN_CPL,
+    IN_SCF,
+    IN_CCF,
+    IN_HALT,
+    IN_ADC,
+    IN_SUB,
+    IN_SBC,
+    IN_AND,
+    IN_XOR,
+    IN_OR,
+    IN_CP,
+    IN_POP,
+    IN_JP,
+    IN_PUSH,
+    IN_RET,
+    IN_CB,
+    IN_CALL,
+    IN_RETI,
+    IN_LDH,
+    IN_JPHL,
+    IN_DI,
+    IN_EI,
+    IN_RST,
+    IN_ERR,
+    //CB instructions...
+    IN_RCL,
+    IN_RRC,
+    IN_RL,
+    IN_RR,
+    IN_SLA,
+    IN_SRA,
+    IN_SWAP,
+    IN_SRL,
+    IN_BIT,
+    IN_RES,
+    IN_SET
+} in_type;
+
+typedef enum {
+    CT_NONE, CT_NZ, CT_Z, CT_NC, CT_C
+} cond_type;
+
+typedef struct {
+    in_type type;
+    addr_mode mode;
+    reg_type reg_1;
+    reg_type reg_2;
+    cond_type cond;
+    u8 param;
+} instruction;
+
+instruction *instruction_by_opcode(u8 opcode);

lib/bus.c

@@ -0,0 +1,32 @@
+#include <bus.h>
+
+// 0x0000 - 0x3FFF : ROM Bank 0
+// 0x4000 - 0x7FFF : ROM Bank 1 - Switchable
+// 0x8000 - 0x97FF : CHR RAM
+// 0x9800 - 0x9BFF : BG Map 1
+// 0x9C00 - 0x9FFF : BG Map 2
+// 0xA000 - 0xBFFF : Cartridge RAM
+// 0xC000 - 0xCFFF : RAM Bank 0
+// 0xD000 - 0xDFFF : RAM Bank 1-7 - switchable - Color only
+// 0xE000 - 0xFDFF : Reserved - Echo RAM
+// 0xFE00 - 0xFE9F : Object Attribute Memory
+// 0xFEA0 - 0xFEFF : Reserved - Unusable
+// 0xFF00 - 0xFF7F : I/O Registers
+// 0xFF80 - 0xFFFE : Zero Page
+
+u8 bus_read(u16 address) {
+    if(address < 0x8000) {
+        return cart_read(address);
+    }
+
+    NO_IMPL
+}
+
+void bus_write(u16 address, u8 value) {
+    if(address < 0x8000) {
+        cart_write(address);
+        return;
+    }
+
+    NO_IMPL
+}

lib/cart.c

@@ -173,4 +173,15 @@ bool cart_load(char *cart) {
     }
     
     return true;
+}
+
+u8 cart_read(u16 address){
+    //for now ROM ONLY type supported...
+
+    return ctx.rom_data[address];
+}
+
+void cart_write(u16 address, u8 value){
+    
+    NO_IMPL
 }

lib/cpu.c

@@ -1,10 +1,64 @@
 #include <cpu.h>
+#include <bus.h>
+
+cpu_context ctx = {0};
 
 void cpu_init() {
+    ctx.regs.pc = 0x100;
+}
 
+static void fetch_instruction() {
+    ctx.cur_opcode = bus_read(ctx.regs.pc++);
+    ctx.cur_inst = instruction_by_opcode(ctx.cur_opcode);
+    if(ctx.cur_inst == NULL){
+        printf("Unknown Instruction! %d\n", ctx.cur_opcode);
+        exit(-7);
+    }
+}
+
+static void fetch_data() {
+    ctx.mem_dest = 0;
+    ctx.dest_is_mem = false;
+
+    switch(ctx.cur_inst->mode) {
+        case AM_IMP: return;
+        case AM_R: 
+            ctx.fetched_data = cpu_read_reg(ctx.cur_inst->reg_1);
+            return;
+        case AM_R_D8:
+            ctx.fetched_data = bus_read(ctx.regs.pc);
+            emu_cycles(1);
+            ctx.regs.pc++;
+            return;
+        case AM_D16: {
+            u16 lo = bus_read(ctx.regs.pc);
+            emu_cycles(1);
+            u16 hi = bus_read(ctx.regs.pc+1);
+            emu_cycles(1);
+            ctx.fetched_data = lo | (hi << 8);
+            ctx.regs.pc += 2;
+            return;
+        }
+        default:
+            printf("Unknown Addressing Mode! %d\n", ctx.cur_inst->mode);
+            exit(-7);
+            return;
+    }
+}
+
+static void execute() {
+    printf("\tNot executing yet...\n");
 }
 
 bool cpu_step() {
-    printf("Cpu not yet implemented.\n");
-    return false;
+    
+    if(!ctx.halted) {
+        u16 pc = ctx.regs.pc;
+        fetch_instruction();
+        fetch_data();
+        printf("Executing Instruction: %02X     PC: %04X\n", ctx.cur_opcode, pc);
+        execute();
+    }
+
+    return true;
 }

lib/cpu_util.c

@@ -0,0 +1,29 @@
+#include <cpu.h>
+
+extern cpu_context ctx;
+
+u16 reverse(u16 n) {
+    return ((n & 0XFF00) >> 8) | ((n & 0x00FF) << 8);
+}
+
+u16 cpu_read_reg(reg_type rt) {
+    switch(rt) {
+        case RT_A: return ctx.regs.a;
+        case RT_F: return ctx.regs.f;
+        case RT_B: return ctx.regs.b;
+        case RT_C: return ctx.regs.c;
+        case RT_D: return ctx.regs.d;
+        case RT_E: return ctx.regs.e;
+        case RT_H: return ctx.regs.h;
+        case RT_L: return ctx.regs.l;
+
+        case RT_AF: return reverse(*((u16 *)&ctx.regs.a));
+        case RT_BC: return reverse(*((u16 *)&ctx.regs.b));
+        case RT_DE: return reverse(*((u16 *)&ctx.regs.d));
+        case RT_HL: return reverse(*((u16 *)&ctx.regs.h));
+
+        case RT_PC: return ctx.regs.pc;
+        case RT_SP: return ctx.regs.sp;
+        default: return 0;
+    }
+}

lib/emu.c

@@ -54,4 +54,8 @@ int emu_run(int argc, char **argv) {
     }
 
     return 0;
+}
+
+void emu_cycles(int cpu_cycles) {
+    //TODO
 }

lib/instructions.c

@@ -0,0 +1,22 @@
+#include <instructions.h>
+#include <cpu.h>
+
+instruction instructions[0x100] = {
+    [0x00] = {IN_NOP, AM_IMP},
+
+    [0x05] = {IN_DEC, AM_R, RT_B},
+
+    [0x0E] = {IN_LD, AM_R_D8, RT_C},
+
+    [0xAF] = {IN_XOR, AM_R, RT_A},
+
+    [0xC3] = {IN_JP, AM_D16},
+};
+
+instruction *instruction_by_opcode(u8 opcode) {
+    if (instructions[opcode].type == IN_NONE) {
+        return NULL;
+    }
+
+    return &instructions[opcode];
+}

tests/test.c

@@ -7,11 +7,6 @@
 #include <cpu.h>
 #include <cart.h>
 
-START_TEST(test_nothing) {
-    bool b = cpu_step();
-    ck_assert_uint_eq(b, false);
-} END_TEST
-
 START_TEST(test_cart) {
     bool b = cart_load("../../roms/cpu_instrs.gb");
     ck_assert_uint_eq(b, true);
@@ -29,7 +24,6 @@ Suite *stack_suite() {
     Suite *s = suite_create("emu");
     TCase *tc = tcase_create("core");
 
-    tcase_add_test(tc, test_nothing);
     tcase_add_test(tc, test_cart);
     suite_add_tcase(s, tc);