From: Joshua Wise <joshua@rebirth.joshuawise.com>
Date: Sun, 30 Mar 2008 09:42:47 +0000 (-0400)
Subject: Our first ALU operation -- ADD
X-Git-Url: http://git.joshuawise.com/fpgaboy.git/commitdiff_plain/94522011a1aecc56d0718817bd4ffeb6b650b308?hp=fa136d635a2e9dea677566536f71e69489dbb200

Our first ALU operation -- ADD
---

diff --git a/FPGABoy.ise b/FPGABoy.ise
index c05d0ea..d4eace8 100644
Binary files a/FPGABoy.ise and b/FPGABoy.ise differ
diff --git a/GBZ80Core.v b/GBZ80Core.v
index b7994ae..0cdefa5 100644
--- a/GBZ80Core.v
+++ b/GBZ80Core.v
@@ -32,6 +32,7 @@
 `define INSN_POP_reg			8'b11xx0001
 `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_reg_A		3'b111
 `define INSN_reg_B		3'b000
@@ -49,6 +50,15 @@
 `define INSN_stack_BC	2'b00
 `define INSN_stack_DE	2'b01
 `define INSN_stack_HL	2'b10
+`define INSN_alu_ADD		3'b000
+`define INSN_alu_ADC		3'b001
+`define INSN_alu_SUB		3'b010
+`define INSN_alu_SBC		3'b011
+`define INSN_alu_AND		3'b100
+`define INSN_alu_XOR		3'b101
+`define INSN_alu_OR		3'b110
+`define INSN_alu_CP		3'b111		// Oh lawd, is dat some CP?
+
 module GBZ80Core(
 	input clk,
 	output reg [15:0] busaddress,	/* BUS_* is latched on STATE_FETCH. */
@@ -303,6 +313,26 @@ module GBZ80Core(
 					end
 				endcase
 			end
+			`INSN_ALU8: begin
+				if ((opcode[2:0] == `INSN_reg_dHL) && (cycle == 0)) begin
+					// fffffffff fuck your shit, read from (HL) :(
+					rd <= 1;
+					address <= {registers[`REG_H], registers[`REG_L]};
+				end else begin
+					`EXEC_NEWCYCLE;
+					`EXEC_INC_PC;
+					case (opcode[2:0])
+					`INSN_reg_A:	begin tmp <= registers[`REG_A]; end
+					`INSN_reg_B:	begin tmp <= registers[`REG_B]; end
+					`INSN_reg_C:	begin tmp <= registers[`REG_C]; end
+					`INSN_reg_D:	begin tmp <= registers[`REG_D]; end
+					`INSN_reg_E:	begin tmp <= registers[`REG_E]; end
+					`INSN_reg_H:	begin tmp <= registers[`REG_H]; end
+					`INSN_reg_L:	begin tmp <= registers[`REG_L]; end
+					`INSN_reg_dHL:	begin tmp <= rdata; end
+					endcase
+				end
+			end
 			default:
 				$stop;
 			endcase
@@ -467,6 +497,28 @@ module GBZ80Core(
 					end
 				endcase
 			end
+			`INSN_ALU8: begin
+				if ((opcode[2:0] == `INSN_reg_dHL) && (cycle == 0)) begin
+					/* Sit on our asses. */
+					cycle <= 1;
+				end else begin		/* Actually do the computation! */
+					case (opcode[5:3])
+					`INSN_alu_ADD: begin
+						registers[`REG_A] <=
+							registers[`REG_A] + tmp;
+						registers[`REG_F] <=
+							{ /* Z */ ((registers[`REG_A] + tmp) == 0) ? 1'b1 : 1'b0,
+							  /* N */ 0,
+							  /* 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]
+							};
+					end
+					default:
+						$stop;
+					endcase
+				end
+			end
 			endcase
 			state <= `STATE_FETCH;
 		end
diff --git a/rom.hex b/rom.hex
index c86844c..6142c98 100644
--- a/rom.hex
+++ b/rom.hex
@@ -6,9 +6,11 @@
 F9
 // POP BC
 C1
-// LD A, 12h
+// LD A, 10h
 3E
-12
+10
+// ADD C
+81
 // LD H, A
 67
 // LD L, 34h
@@ -20,5 +22,5 @@ C1
 76
 
 @100
-50
+02
 56