branch opcodes

3 files changed, 64 insertions, 1 deletions

diff --git a/CPU.c b/CPU.c
index b44a84c..4e7dfa1 100644
--- a/CPU.c
+++ b/CPU.c
@@ -2,6 +2,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <assert.h>
+#include <stdbool.h>
 #include "CPU.h"
 #include "opcode_pc.h"
 
@@ -170,6 +171,17 @@ void disable_flag(struct CPU *cpu, uint8_t flag){
     cpu->status &= !flag;
 }
 
+int test_flag(struct CPU *cpu, uint8_t flag){
+    return (flag & cpu->status) > 0;
+}
+
+void branch(struct CPU *cpu, bool cond){
+    if(cond){
+        int8_t jump = mem_read(cpu, cpu->pc);
+        cpu->pc = (cpu->pc + jump + 1) % 0x10000;
+    }
+}
+
 void asl(struct CPU *cpu, enum adressing_mode mode){
     uint16_t addr = get_operand_address(cpu, mode);
     uint8_t value = mem_read(cpu, addr);
@@ -222,6 +234,31 @@ void interpret(struct CPU *cpu){
                     asl(cpu, OPCODE[opcode].mode);
                 }
                 cpu->pc += OPCODE[opcode].bytes - 1;
+                break;
+            case BCC:
+                branch(cpu, !test_flag(cpu, CARRY));
+                break;
+            case BCS:
+                branch(cpu, test_flag(cpu, CARRY));
+                break;
+            case BEQ:
+                branch(cpu, test_flag(cpu, ZERO));
+                break;
+            case BMI:
+                branch(cpu, test_flag(cpu, NEGATIV));
+                break;
+            case BNE:
+                branch(cpu, !test_flag(cpu, ZERO));
+                break;
+            case BPL:
+                branch(cpu, !test_flag(cpu, NEGATIV));
+                break;
+            case BVC:
+                branch(cpu, !test_flag(cpu, OVERFLOW));
+                break;
+            case BVS:
+                branch(cpu, test_flag(cpu, OVERFLOW));
+                break;
             default:
                 break;
         }
diff --git a/CPU.h b/CPU.h
index 4600621..5069ab3 100644
--- a/CPU.h
+++ b/CPU.h
@@ -49,7 +49,9 @@ uint16_t get_operand_address(struct CPU *cpu, enum adressing_mode mode);
 void and(struct CPU *cpu, enum adressing_mode mode);
 void enable_flag(struct CPU *cpu, uint8_t flag);
 void disable_flag(struct CPU *cpu, uint8_t flag);
+int test_flag(struct CPU *cpu, uint8_t flag);
 void asl(struct CPU *cpu, enum adressing_mode mode);
+void branch(struct CPU *cpu, bool cond);
 
 
 #endif
\ No newline at end of file
diff --git a/opcode_pc.h b/opcode_pc.h
index 7a79bbe..0d79aad 100644
--- a/opcode_pc.h
+++ b/opcode_pc.h
@@ -11,6 +11,14 @@ enum _INSTRUCTION{
     INX,
     AND,
     ASL,
+    BCC,
+    BCS,
+    BEQ,
+    BMI,
+    BNE,
+    BPL,
+    BVC,
+    BVS,
 };
 
 struct _OPCODE{
@@ -57,7 +65,23 @@ void init_opcode_pc(){
     OPCODE[0x06] = (struct _OPCODE){ASL, ZeroPage, 2};
     OPCODE[0x16] = (struct _OPCODE){ASL, ZeroPage_X, 2};
     OPCODE[0x0E] = (struct _OPCODE){ASL, Absolute, 3};
-    OPCODE[0x1E] = (struct _OPCODE){ASL, Absolute_X, 3};    
+    OPCODE[0x1E] = (struct _OPCODE){ASL, Absolute_X, 3};   
+    /*BCC*/
+    OPCODE[0x90] = (struct _OPCODE){BCC, NoneAddressing, 2}; 
+    /*BCS*/
+    OPCODE[0xB0] = (struct _OPCODE){BCS, NoneAddressing, 2};
+    /*BEQ*/
+    OPCODE[0xF0] = (struct _OPCODE){BEQ, NoneAddressing, 2};
+    /*BMI*/
+    OPCODE[0x30] = (struct _OPCODE){BMI, NoneAddressing, 2};
+    /*BNE*/
+    OPCODE[0xD0] = (struct _OPCODE){BNE, NoneAddressing, 2};
+    /*BPL*/
+    OPCODE[0x10] = (struct _OPCODE){BPL, NoneAddressing, 2};
+    /*BVC*/
+    OPCODE[0x50] = (struct _OPCODE){BVC, NoneAddressing, 2};
+    /*BVS*/
+    OPCODE[0x70] = (struct _OPCODE){BVS, NoneAddressing, 2};
 }
 
 #endif
\ No newline at end of file