Finish splitting out functions.

[fpgaboy.git] / insn_alu8.v

`ifdef EXECUTE
	`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:	tmp <= registers[`REG_A];
			`INSN_reg_B:	tmp <= registers[`REG_B];
			`INSN_reg_C:	tmp <= registers[`REG_C];
			`INSN_reg_D:	tmp <= registers[`REG_D];
			`INSN_reg_E:	tmp <= registers[`REG_E];
			`INSN_reg_H:	tmp <= registers[`REG_H];
			`INSN_reg_L:	tmp <= registers[`REG_L];
			`INSN_reg_dHL:	tmp <= rdata;
			endcase
		end
	end
`endif

`ifdef WRITEBACK
	`INSN_ALU8: begin
		if ((opcode[2:0] == `INSN_reg_dHL) && (cycle == 0)) begin
			/* Sit on our asses. */
		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 */ 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]
					};
			end
			`INSN_alu_ADC: begin
				registers[`REG_A] <=
					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 */ 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]
					};
			end
			`INSN_alu_SUB: begin
				registers[`REG_A] <=
					registers[`REG_A] - tmp;
				registers[`REG_F] <=
					{ /* Z */ ((registers[`REG_A] - tmp) == 0) ? 1'b1 : 1'b0,
					  /* N */ 1'b1,
					  /* 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
			`INSN_alu_SBC: begin
				registers[`REG_A] <=
					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 */ 1'b1,
					  /* 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]
					};
			end
			`INSN_alu_AND: begin
				registers[`REG_A] <=
					registers[`REG_A] & tmp;
				registers[`REG_F] <=
					{ /* Z */ ((registers[`REG_A] & tmp) == 0) ? 1'b1 : 1'b0,
					  3'b010,
					  registers[`REG_F][3:0]
					};
			end
			`INSN_alu_OR: begin
				registers[`REG_A] <=
					registers[`REG_A] | tmp;
				registers[`REG_F] <=
					{ /* Z */ ((registers[`REG_A] | tmp) == 0) ? 1'b1 : 1'b0,
					  3'b000,
					  registers[`REG_F][3:0]
					};
			end
			`INSN_alu_XOR: begin
				registers[`REG_A] <=
					registers[`REG_A] ^ tmp;
				registers[`REG_F] <=
					{ /* Z */ ((registers[`REG_A] ^ tmp) == 0) ? 1'b1 : 1'b0,
					  3'b000,
					  registers[`REG_F][3:0]
					};
			end
			`INSN_alu_CP: begin
				registers[`REG_F] <=
					{ /* Z */ ((registers[`REG_A] - tmp) == 0) ? 1'b1 : 1'b0,
					  /* N */ 1'b1,
					  /* 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
`endif