NOP, and bug fixes

[fpgaboy.git] / GBZ80Core.v

diff --git a/GBZ80Core.v b/GBZ80Core.v
index 1aaa01c9fce246300e4aa50372055767ff268533..3e15ebf255f473dc239bf89e4b878ad3bcb02087 100644 (file)
--- a/GBZ80Core.v
+++ b/GBZ80Core.v
@@ -33,6 +33,7 @@
 `define INSN_LDH_AC                    8'b111x0010     // Either LDH A,(C) or LDH (C),A
 `define INSN_LDx_AHL                   8'b001xx010     // LDD/LDI A,(HL) / (HL),A
 `define INSN_ALU8                              8'b10xxxxxx     // 10 xxx yyy
+`define INSN_NOP                               8'b00000000
 
 `define INSN_reg_A             3'b111
 `define INSN_reg_B             3'b000
@@ -333,6 +334,10 @@ module GBZ80Core(
                                        endcase
                                end
                        end
+                       `INSN_NOP: begin
+                               `EXEC_NEWCYCLE;
+                               `EXEC_INC_PC;
+                       end
                        default:
                                $stop;
                        endcase
@@ -508,7 +513,7 @@ module GBZ80Core(
                                                        registers[`REG_A] + tmp;
                                                registers[`REG_F] <=
                                                        { /* Z */ ((registers[`REG_A] + tmp) == 0) ? 1'b1 : 1'b0,
-                                                         /* N */ 0,
+                                                         /* N */ 1'b0,
                                                          /* H */ (({1'b0,registers[`REG_A][3:0]} + {1'b0,tmp[3:0]}) >> 4 == 1) ? 1'b1 : 1'b0,
                                                          /* C */ (({1'b0,registers[`REG_A]} + {1'b0,tmp}) >> 8 == 1) ? 1'b1 : 1'b0,
                                                          registers[`REG_F][3:0]
@@ -519,7 +524,7 @@ module GBZ80Core(
                                                        registers[`REG_A] + tmp + {7'b0,registers[`REG_F][4]};
                                                registers[`REG_F] <=
                                                        { /* Z */ ((registers[`REG_A] + tmp + {7'b0,registers[`REG_F][4]}) == 0) ? 1'b1 : 1'b0,
-                                                         /* N */ 0,
+                                                         /* N */ 1'b0,
                                                          /* H */ (({1'b0,registers[`REG_A][3:0]} + {1'b0,tmp[3:0]} + {4'b0,registers[`REG_F][4]}) >> 4 == 1) ? 1'b1 : 1'b0,
                                                          /* C */ (({1'b0,registers[`REG_A]} + {1'b0,tmp} + {8'b0,registers[`REG_F][4]}) >> 8 == 1) ? 1'b1 : 1'b0,
                                                          registers[`REG_F][3:0]
@@ -530,7 +535,7 @@ module GBZ80Core(
                                                        registers[`REG_A] & tmp;
                                                registers[`REG_F] <=
                                                        { /* Z */ ((registers[`REG_A] & tmp) == 0) ? 1'b1 : 1'b0,
-                                                         0,1,0,
+                                                         3'b010,
                                                          registers[`REG_F][3:0]
                                                        };
                                        end
@@ -539,7 +544,7 @@ module GBZ80Core(
                                                        registers[`REG_A] | tmp;
                                                registers[`REG_F] <=
                                                        { /* Z */ ((registers[`REG_A] | tmp) == 0) ? 1'b1 : 1'b0,
-                                                         0,0,0,
+                                                         3'b000,
                                                          registers[`REG_F][3:0]
                                                        };
                                        end
@@ -548,7 +553,7 @@ module GBZ80Core(
                                                        registers[`REG_A] ^ tmp;
                                                registers[`REG_F] <=
                                                        { /* Z */ ((registers[`REG_A] ^ tmp) == 0) ? 1'b1 : 1'b0,
-                                                         0,0,0,
+                                                         3'b000,
                                                          registers[`REG_F][3:0]
                                                        };
                                        end
@@ -557,6 +562,7 @@ module GBZ80Core(
                                        endcase
                                end
                        end
+                       `INSN_NOP: begin /* NOP! */ end
                        endcase
                        state <= `STATE_FETCH;
                end