t80_mcode.vhd

DE1-FPGA-Board

					IncDec_16 <= "0110";
				when others => null;
				end case;
			else
				-- LD (nn),HL
				MCycles <= "101";
				case to_integer(unsigned(MCycle)) is
				when 2 =>
					Inc_PC <= '1';
					LDZ <= '1';
				when 3 =>
					Set_Addr_To <= aZI;
					Inc_PC <= '1';
					LDW <= '1';
					Set_BusB_To <= "0101"; -- L
				when 4 =>
					Inc_WZ <= '1';
					Set_Addr_To <= aZI;
					Write <= '1';
					Set_BusB_To <= "0100"; -- H
				when 5 =>
					Write <= '1';
				when others => null;
				end case;
			end if;
		when "11111001" =>
			-- LD SP,HL
			TStates <= "110";
			LDSPHL <= '1';
		when "11000101"|"11010101"|"11100101"|"11110101" =>
			-- PUSH qq
			MCycles <= "011";
			case to_integer(unsigned(MCycle)) is
			when 1 =>
				TStates <= "101";
				IncDec_16 <= "1111";
				Set_Addr_TO <= aSP;
				if DPAIR = "11" then
					Set_BusB_To <= "0111";
				else
					Set_BusB_To(2 downto 1) <= DPAIR;
					Set_BusB_To(0) <= '0';
					Set_BusB_To(3) <= '0';
				end if;
			when 2 =>
				IncDec_16 <= "1111";
				Set_Addr_To <= aSP;
				if DPAIR = "11" then
					Set_BusB_To <= "1011";
				else
					Set_BusB_To(2 downto 1) <= DPAIR;
					Set_BusB_To(0) <= '1';
					Set_BusB_To(3) <= '0';
				end if;
				Write <= '1';
			when 3 =>
				Write <= '1';
			when others => null;
			end case;
		when "11000001"|"11010001"|"11100001"|"11110001" =>
			-- POP qq
			MCycles <= "011";
			case to_integer(unsigned(MCycle)) is
			when 1 =>
				Set_Addr_To <= aSP;
			when 2 =>
				IncDec_16 <= "0111";
				Set_Addr_To <= aSP;
				Read_To_Reg <= '1';
				if DPAIR = "11" then
					Set_BusA_To(3 downto 0) <= "1011";
				else
					Set_BusA_To(2 downto 1) <= DPAIR;
					Set_BusA_To(0) <= '1';
				end if;
			when 3 =>
				IncDec_16 <= "0111";
				Read_To_Reg <= '1';
				if DPAIR = "11" then
					Set_BusA_To(3 downto 0) <= "0111";
				else
					Set_BusA_To(2 downto 1) <= DPAIR;
					Set_BusA_To(0) <= '0';
				end if;
			when others => null;
			end case;

-- EXCHANGE, BLOCK TRANSFER AND SEARCH GROUP
		when "11101011" =>
			if Mode /= 3 then
				-- EX DE,HL
				ExchangeDH <= '1';
			end if;
		when "00001000" =>
			if Mode = 3 then
				-- LD (nn),SP
				MCycles <= "101";
				case to_integer(unsigned(MCycle)) is
				when 2 =>
					Inc_PC <= '1';
					LDZ <= '1';
				when 3 =>
					Set_Addr_To <= aZI;
					Inc_PC <= '1';
					LDW <= '1';
					Set_BusB_To <= "1000";
				when 4 =>
					Inc_WZ <= '1';
					Set_Addr_To <= aZI;
					Write <= '1';
					Set_BusB_To <= "1001";
				when 5 =>
					Write <= '1';
				when others => null;
				end case;
			elsif Mode < 2 then
				-- EX AF,AF'
				ExchangeAF <= '1';
			end if;
		when "11011001" =>
			if Mode = 3 then
				-- RETI
				MCycles <= "011";
				case to_integer(unsigned(MCycle)) is
				when 1 =>
					Set_Addr_TO <= aSP;
				when 2 =>
					IncDec_16 <= "0111";
					Set_Addr_To <= aSP;
					LDZ <= '1';
				when 3 =>
					Jump <= '1';
					IncDec_16 <= "0111";
					I_RETN <= '1';
					SetEI <= '1';
				when others => null;
				end case;
			elsif Mode < 2 then
				-- EXX
				ExchangeRS <= '1';
			end if;
		when "11100011" =>
			if Mode /= 3 then
				-- EX (SP),HL
				MCycles <= "101";
				case to_integer(unsigned(MCycle)) is
				when 1 =>
					Set_Addr_To <= aSP;
				when 2 =>
					Read_To_Reg <= '1';
					Set_BusA_To <= "0101";
					Set_BusB_To <= "0101";
					Set_Addr_To <= aSP;
				when 3 =>
					IncDec_16 <= "0111";
					Set_Addr_To <= aSP;
					TStates <= "100";
					Write <= '1';
				when 4 =>
					Read_To_Reg <= '1';
					Set_BusA_To <= "0100";
					Set_BusB_To <= "0100";
					Set_Addr_To <= aSP;
				when 5 =>
					IncDec_16 <= "1111";
					TStates <= "101";
					Write <= '1';
				when others => null;
				end case;
			end if;

-- 8 BIT ARITHMETIC AND LOGICAL GROUP
		when "10000000"|"10000001"|"10000010"|"10000011"|"10000100"|"10000101"|"10000111"
			|"10001000"|"10001001"|"10001010"|"10001011"|"10001100"|"10001101"|"10001111"
			|"10010000"|"10010001"|"10010010"|"10010011"|"10010100"|"10010101"|"10010111"
			|"10011000"|"10011001"|"10011010"|"10011011"|"10011100"|"10011101"|"10011111"
			|"10100000"|"10100001"|"10100010"|"10100011"|"10100100"|"10100101"|"10100111"
			|"10101000"|"10101001"|"10101010"|"10101011"|"10101100"|"10101101"|"10101111"
			|"10110000"|"10110001"|"10110010"|"10110011"|"10110100"|"10110101"|"10110111"
			|"10111000"|"10111001"|"10111010"|"10111011"|"10111100"|"10111101"|"10111111" =>
			-- ADD A,r
			-- ADC A,r
			-- SUB A,r
			-- SBC A,r
			-- AND A,r
			-- OR A,r
			-- XOR A,r
			-- CP A,r
			Set_BusB_To(2 downto 0) <= SSS;
			Set_BusA_To(2 downto 0) <= "111";
			Read_To_Reg <= '1';
			Save_ALU <= '1';
		when "10000110"|"10001110"|"10010110"|"10011110"|"10100110"|"10101110"|"10110110"|"10111110" =>
			-- ADD A,(HL)
			-- ADC A,(HL)
			-- SUB A,(HL)
			-- SBC A,(HL)
			-- AND A,(HL)
			-- OR A,(HL)
			-- XOR A,(HL)
			-- CP A,(HL)
			MCycles <= "010";
			case to_integer(unsigned(MCycle)) is
			when 1 =>
				Set_Addr_To <= aXY;
			when 2 =>
				Read_To_Reg <= '1';
				Save_ALU <= '1';
				Set_BusB_To(2 downto 0) <= SSS;
				Set_BusA_To(2 downto 0) <= "111";
			when others => null;
			end case;
		when "11000110"|"11001110"|"11010110"|"11011110"|"11100110"|"11101110"|"11110110"|"11111110" =>
			-- ADD A,n
			-- ADC A,n
			-- SUB A,n
			-- SBC A,n
			-- AND A,n
			-- OR A,n
			-- XOR A,n
			-- CP A,n
			MCycles <= "010";
			if MCycle = "010" then
				Inc_PC <= '1';
				Read_To_Reg <= '1';
				Save_ALU <= '1';
				Set_BusB_To(2 downto 0) <= SSS;
				Set_BusA_To(2 downto 0) <= "111";
			end if;
		when "00000100"|"00001100"|"00010100"|"00011100"|"00100100"|"00101100"|"00111100" =>
			-- INC r
			Set_BusB_To <= "1010";
			Set_BusA_To(2 downto 0) <= DDD;
			Read_To_Reg <= '1';
			Save_ALU <= '1';
			PreserveC <= '1';
			ALU_Op <= "0000";
		when "00110100" =>
			-- INC (HL)
			MCycles <= "011";
			case to_integer(unsigned(MCycle)) is
			when 1 =>
				Set_Addr_To <= aXY;
			when 2 =>
				TStates <= "100";
				Set_Addr_To <= aXY;
				Read_To_Reg <= '1';
				Save_ALU <= '1';
				PreserveC <= '1';
				ALU_Op <= "0000";
				Set_BusB_To <= "1010";
				Set_BusA_To(2 downto 0) <= DDD;
			when 3 =>
				Write <= '1';
			when others => null;
			end case;
		when "00000101"|"00001101"|"00010101"|"00011101"|"00100101"|"00101101"|"00111101" =>
			-- DEC r
			Set_BusB_To <= "1010";
			Set_BusA_To(2 downto 0) <= DDD;
			Read_To_Reg <= '1';
			Save_ALU <= '1';
			PreserveC <= '1';
			ALU_Op <= "0010";
		when "00110101" =>
			-- DEC (HL)
			MCycles <= "011";
			case to_integer(unsigned(MCycle)) is
			when 1 =>
				Set_Addr_To <= aXY;
			when 2 =>
				TStates <= "100";
				Set_Addr_To <= aXY;
				ALU_Op <= "0010";
				Read_To_Reg <= '1';
				Save_ALU <= '1';
				PreserveC <= '1';
				Set_BusB_To <= "1010";
				Set_BusA_To(2 downto 0) <= DDD;
			when 3 =>
				Write <= '1';
			when others => null;
			end case;

-- GENERAL PURPOSE ARITHMETIC AND CPU CONTROL GROUPS
		when "00100111" =>
			-- DAA
			Set_BusA_To(2 downto 0) <= "111";
			Read_To_Reg <= '1';
			ALU_Op <= "1100";
			Save_ALU <= '1';
		when "00101111" =>
			-- CPL
			I_CPL <= '1';
		when "00111111" =>
			-- CCF
			I_CCF <= '1';
		when "00110111" =>
			-- SCF
			I_SCF <= '1';
		when "00000000" =>
			if NMICycle = '1' then
				-- NMI
				MCycles <= "011";
				case to_integer(unsigned(MCycle)) is
				when 1 =>
					TStates <= "101";
					IncDec_16 <= "1111";
					Set_Addr_To <= aSP;
					Set_BusB_To <= "1101";
				when 2 =>
					TStates <= "100";
					Write <= '1';
					IncDec_16 <= "1111";
					Set_Addr_To <= aSP;
					Set_BusB_To <= "1100";
				when 3 =>
					TStates <= "100";
					Write <= '1';
				when others => null;
				end case;
			elsif IntCycle = '1' then
				-- INT (IM 2)
				MCycles <= "101";
				case to_integer(unsigned(MCycle)) is
				when 1 =>
					LDZ <= '1';
					TStates <= "101";
					IncDec_16 <= "1111";
					Set_Addr_To <= aSP;
					Set_BusB_To <= "1101";
				when 2 =>
					TStates <= "100";
					Write <= '1';
					IncDec_16 <= "1111";
					Set_Addr_To <= aSP;
					Set_BusB_To <= "1100";
				when 3 =>
					TStates <= "100";
					Write <= '1';
				when 4 =>
					Inc_PC <= '1';
					LDZ <= '1';
				when 5 =>
					Jump <= '1';
				when others => null;
				end case;
			else
				-- NOP
			end if;
		when "01110110" =>
			-- HALT
			Halt <= '1';
		when "11110011" =>
			-- DI
			SetDI <= '1';
		when "11111011" =>
			-- EI
			SetEI <= '1';

-- 16 BIT ARITHMETIC GROUP
		when "00001001"|"00011001"|"00101001"|"00111001" =>
			-- ADD HL,ss
			MCycles <= "011";
			case to_integer(unsigned(MCycle)) is
			when 2 =>
				NoRead <= '1';
				ALU_Op <= "0000";
				Read_To_Reg <= '1';
				Save_ALU <= '1';
				Set_BusA_To(2 downto 0) <= "101";
				case to_integer(unsigned(IR(5 downto 4))) is
				when 0|1|2 =>
					Set_BusB_To(2 downto 1) <= IR(5 downto 4);
					Set_BusB_To(0) <= '1';
				when others =>
					Set_BusB_To <= "1000";
				end case;
				TStates <= "100";
				Arith16 <= '1';
			when 3 =>
				NoRead <= '1';
				Read_To_Reg <= '1';
				Save_ALU <= '1';
				ALU_Op <= "0001";
				Set_BusA_To(2 downto 0) <= "100";
				case to_integer(unsigned(IR(5 downto 4))) is
				when 0|1|2 =>
					Set_BusB_To(2 downto 1) <= IR(5 downto 4);
				when others =>
					Set_BusB_To <= "1001";
				end case;
				Arith16 <= '1';
			when others =>
			end case;
		when "00000011"|"00010011"|"00100011"|"00110011" =>
			-- INC ss
			TStates <= "110";
			IncDec_16(3 downto 2) <= "01";
			IncDec_16(1 downto 0) <= DPair;
		when "00001011"|"00011011"|"00101011"|"00111011" =>
			-- DEC ss
			TStates <= "110";
			IncDec_16(3 downto 2) <= "11";
			IncDec_16(1 downto 0) <= DPair;

-- ROTATE AND SHIFT GROUP
		when "00000111"
			-- RLCA
			|"00010111"
			-- RLA
			|"00001111"
			-- RRCA
			|"00011111" =>
			-- RRA
			Set_BusA_To(2 downto 0) <= "111";
			ALU_Op <= "1000";
			Read_To_Reg <= '1';
			Save_ALU <= '1';

-- JUMP GROUP
		when "11000011" =>
			-- JP nn
			MCycles <= "011";
			case to_integer(unsigned(MCycle)) is
			when 2 =>
				Inc_PC <= '1';
				LDZ <= '1';
			when 3 =>
				Inc_PC <= '1';
				Jump <= '1';
			when others => null;
			end case;
		when "11000010"|"11001010"|"11010010"|"11011010"|"11100010"|"11101010"|"11110010"|"11111010" =>
			if IR(5) = '1' and Mode = 3 then
				case IRB(4 downto 3) is
				when "00" =>
					-- LD ($FF00+C),A
					MCycles <= "010";
					case to_integer(unsigned(MCycle)) is
					when 1 =>
						Set_Addr_To <= aBC;
						Set_BusB_To	<= "0111";
					when 2 =>
						Write <= '1';
						IORQ <= '1';
					when others =>
					end case;
				when "01" =>
					-- LD (nn),A
					MCycles <= "100";
					case to_integer(unsigned(MCycle)) is
					when 2 =>
						Inc_PC <= '1';
						LDZ <= '1';
					when 3 =>
						Set_Addr_To <= aZI;
						Inc_PC <= '1';
						Set_BusB_To <= "0111";
					when 4 =>
						Write <= '1';
					when others => null;
					end case;
				when "10" =>
					-- LD A,($FF00+C)
					MCycles <= "010";
					case to_integer(unsigned(MCycle)) is
					when 1 =>
						Set_Addr_To <= aBC;
					when 2 =>
						Read_To_Acc <= '1';
						IORQ <= '1';
					when others =>
					end case;
				when "11" =>
					-- LD A,(nn)
					MCycles <= "100";
					case to_integer(unsigned(MCycle)) is
					when 2 =>
						Inc_PC <= '1';
						LDZ <= '1';
					when 3 =>
						Set_Addr_To <= aZI;
						Inc_PC <= '1';