X-Git-Url: http://git.joshuawise.com/fpgaboy.git/blobdiff_plain/77ab69d7bb0902e6ebf0994159ed2205f8413e34..b057a5d6e6db6db06ae33703ca72cd235eec91d6:/core/insn_alu8.v

diff --git a/core/insn_alu8.v b/core/insn_alu8.v
new file mode 100644
index 0000000..2921b18
--- /dev/null
+++ b/core/insn_alu8.v
@@ -0,0 +1,101 @@
+`ifdef EXECUTE
+	`INSN_ALU8,`INSN_ALU8IMM: begin
+		if ((opcode[7:6] == 2'b11) && (cycle == 0)) begin	// alu8imm
+			`EXEC_INC_PC
+			`EXEC_READ(`_PC + 1)
+		end else if ((opcode[2:0] == `INSN_reg_dHL) && (cycle == 0))
+			`EXEC_READ(`_HL)
+		else begin
+			`EXEC_NEWCYCLE
+			`EXEC_INC_PC
+			case (opcode[2:0])
+			`INSN_reg_A:	tmp <= `_A;
+			`INSN_reg_B:	tmp <= `_B;
+			`INSN_reg_C:	tmp <= `_C;
+			`INSN_reg_D:	tmp <= `_D;
+			`INSN_reg_E:	tmp <= `_E;
+			`INSN_reg_H:	tmp <= `_H;
+			`INSN_reg_L:	tmp <= `_L;
+			`INSN_reg_dHL:	tmp <= rdata;
+			endcase
+		end
+	end
+`endif
+
+`ifdef WRITEBACK
+	`INSN_ALU8,`INSN_ALU8IMM: begin
+		if (((opcode[2:0] == `INSN_reg_dHL) || (opcode[7:6] == 2'b11)) && (cycle == 0)) begin
+			/* Sit on our asses. */
+		end else begin		/* Actually do the computation! */
+			case (opcode[5:3])
+			`INSN_alu_ADD: begin
+				`_A <= `_A + tmp;
+				`_F <=	{ /* Z */ ((`_A + tmp) == 8'b0) ? 1'b1 : 1'b0,
+					  /* N */ 1'b0,
+					  /* H */ (({1'b0,`_A[3:0]} + {1'b0,tmp[3:0]}) >> 4 == 1) ? 1'b1 : 1'b0,
+					  /* C */ (({1'b0,`_A} + {1'b0,tmp}) >> 8 == 1) ? 1'b1 : 1'b0,
+					  `_F[3:0]
+					};
+			end
+			`INSN_alu_ADC: begin
+				`_A <= `_A + tmp + {7'b0,`_F[4]};
+				`_F <=	{ /* Z */ ((`_A + tmp + {7'b0,`_F[4]}) == 8'b0) ? 1'b1 : 1'b0,
+					  /* N */ 1'b0,
+					  /* H */ (({1'b0,`_A[3:0]} + {1'b0,tmp[3:0]} + {4'b0,`_F[4]}) >> 4 == 1) ? 1'b1 : 1'b0,
+					  /* C */ (({1'b0,`_A} + {1'b0,tmp} + {8'b0,`_F[4]}) >> 8 == 1) ? 1'b1 : 1'b0,
+					  `_F[3:0]
+					};
+			end
+			`INSN_alu_SUB: begin
+				`_A <= `_A - tmp;
+				`_F <=	{ /* Z */ (`_A == tmp) ? 1'b1 : 1'b0,
+					  /* N */ 1'b1,
+					  /* H */ (tmp[3:0] > `_A[3:0]) ? 1'b1 : 1'b0,
+					  /* C */ (tmp > `_A) ? 1'b1 : 1'b0,
+					  `_F[3:0]
+					};
+			end
+			`INSN_alu_SBC: begin
+				`_A <= `_A - (tmp + {7'b0,`_F[4]});
+				`_F <= 	{ /* Z */ ((`_A - (tmp + {7'b0,`_F[4]})) == 8'b0) ? 1'b1 : 1'b0,
+					  /* N */ 1'b1,
+					  /* H */ (({1'b0,tmp[3:0]} + {4'b0,`_F[4]}) > {1'b0,`_A[3:0]}) ? 1'b1 : 1'b0,
+					  /* C */ (({1'b0,tmp} + {8'b0,`_F[4]}) > {1'b0,`_A[7:0]}) ? 1'b1 : 1'b0,
+					  `_F[3:0]
+					};
+			end
+			`INSN_alu_AND: begin
+				`_A <= `_A & tmp;
+				`_F <=	{ /* Z */ ((`_A & tmp) == 0) ? 1'b1 : 1'b0,
+					  3'b010,
+					  `_F[3:0]
+					};
+			end
+			`INSN_alu_OR: begin
+				`_A <= `_A | tmp;
+				`_F <=	{ /* Z */ ((`_A | tmp) == 0) ? 1'b1 : 1'b0,
+					  3'b000,
+					  `_F[3:0]
+					};
+			end
+			`INSN_alu_XOR: begin
+				`_A <= `_A ^ tmp;
+				`_F <=	{ /* Z */ ((`_A ^ tmp) == 0) ? 1'b1 : 1'b0,
+					  3'b000,
+					  `_F[3:0]
+					};
+			end
+			`INSN_alu_CP: begin
+				`_F <=	{ /* Z */ (`_A == tmp) ? 1'b1 : 1'b0,
+					  /* N */ 1'b1,
+					  /* H */ (tmp[3:0] > `_A[3:0]) ? 1'b1 : 1'b0,
+					  /* C */ (tmp > `_A) ? 1'b1 : 1'b0,
+					  `_F[3:0]
+					};
+			end
+			default:
+				$stop;
+			endcase
+		end
+	end
+`endif