t80_mcode.vhd

DE1-FPGA-Board

				if MCycle = "001" then
					ALU_Op <= "1011";
					Read_To_Reg <= '1';
					Save_ALU <= '1';
				end if;
			when "10000110"|"10001110"|"10010110"|"10011110"|"10100110"|"10101110"|"10110110"|"10111110" =>
				-- RES b,(HL)
				MCycles <= "011";
				case to_integer(unsigned(MCycle)) is
				when 1 | 7 =>
					Set_Addr_To <= aXY;
				when 2 =>
					ALU_Op <= "1011";
					Read_To_Reg <= '1';
					Save_ALU <= '1';
					Set_Addr_To <= aXY;
					TStates <= "100";
				when 3 =>
					Write <= '1';
				when others =>
				end case;
			end case;

		when others =>

------------------------------------------------------------------------------
--
--	ED prefixed instructions
--
------------------------------------------------------------------------------

			case IRB is
			when "00000000"|"00000001"|"00000010"|"00000011"|"00000100"|"00000101"|"00000110"|"00000111"
				|"00001000"|"00001001"|"00001010"|"00001011"|"00001100"|"00001101"|"00001110"|"00001111"
				|"00010000"|"00010001"|"00010010"|"00010011"|"00010100"|"00010101"|"00010110"|"00010111"
				|"00011000"|"00011001"|"00011010"|"00011011"|"00011100"|"00011101"|"00011110"|"00011111"
				|"00100000"|"00100001"|"00100010"|"00100011"|"00100100"|"00100101"|"00100110"|"00100111"
				|"00101000"|"00101001"|"00101010"|"00101011"|"00101100"|"00101101"|"00101110"|"00101111"
				|"00110000"|"00110001"|"00110010"|"00110011"|"00110100"|"00110101"|"00110110"|"00110111"
				|"00111000"|"00111001"|"00111010"|"00111011"|"00111100"|"00111101"|"00111110"|"00111111"


				|"10000000"|"10000001"|"10000010"|"10000011"|"10000100"|"10000101"|"10000110"|"10000111"
				|"10001000"|"10001001"|"10001010"|"10001011"|"10001100"|"10001101"|"10001110"|"10001111"
				|"10010000"|"10010001"|"10010010"|"10010011"|"10010100"|"10010101"|"10010110"|"10010111"
				|"10011000"|"10011001"|"10011010"|"10011011"|"10011100"|"10011101"|"10011110"|"10011111"
				|                                            "10100100"|"10100101"|"10100110"|"10100111"
				|                                            "10101100"|"10101101"|"10101110"|"10101111"
				|                                            "10110100"|"10110101"|"10110110"|"10110111"
				|                                            "10111100"|"10111101"|"10111110"|"10111111"
				|"11000000"|"11000001"|"11000010"|"11000011"|"11000100"|"11000101"|"11000110"|"11000111"
				|"11001000"|"11001001"|"11001010"|"11001011"|"11001100"|"11001101"|"11001110"|"11001111"
				|"11010000"|"11010001"|"11010010"|"11010011"|"11010100"|"11010101"|"11010110"|"11010111"
				|"11011000"|"11011001"|"11011010"|"11011011"|"11011100"|"11011101"|"11011110"|"11011111"
				|"11100000"|"11100001"|"11100010"|"11100011"|"11100100"|"11100101"|"11100110"|"11100111"
				|"11101000"|"11101001"|"11101010"|"11101011"|"11101100"|"11101101"|"11101110"|"11101111"
				|"11110000"|"11110001"|"11110010"|"11110011"|"11110100"|"11110101"|"11110110"|"11110111"
				|"11111000"|"11111001"|"11111010"|"11111011"|"11111100"|"11111101"|"11111110"|"11111111" =>
				null; -- NOP, undocumented
			when "01111110"|"01111111" =>
				-- NOP, undocumented
				null;
-- 8 BIT LOAD GROUP
			when "01010111" =>
				-- LD A,I
				Special_LD <= "100";
				TStates <= "101";
			when "01011111" =>
				-- LD A,R
				Special_LD <= "101";
				TStates <= "101";
			when "01000111" =>
				-- LD I,A
				Special_LD <= "110";
				TStates <= "101";
			when "01001111" =>
				-- LD R,A
				Special_LD <= "111";
				TStates <= "101";
-- 16 BIT LOAD GROUP
			when "01001011"|"01011011"|"01101011"|"01111011" =>
				-- LD dd,(nn)
				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';
				when 4 =>
					Read_To_Reg <= '1';
					if IR(5 downto 4) = "11" then
						Set_BusA_To <= "1000";
					else
						Set_BusA_To(2 downto 1) <= IR(5 downto 4);
						Set_BusA_To(0) <= '1';
					end if;
					Inc_WZ <= '1';
					Set_Addr_To <= aZI;
				when 5 =>
					Read_To_Reg <= '1';
					if IR(5 downto 4) = "11" then
						Set_BusA_To <= "1001";
					else
						Set_BusA_To(2 downto 1) <= IR(5 downto 4);
						Set_BusA_To(0) <= '0';
					end if;
				when others => null;
				end case;
			when "01000011"|"01010011"|"01100011"|"01110011" =>
				-- LD (nn),dd
				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';
					if IR(5 downto 4) = "11" then
						Set_BusB_To <= "1000";
					else
						Set_BusB_To(2 downto 1) <= IR(5 downto 4);
						Set_BusB_To(0) <= '1';
						Set_BusB_To(3) <= '0';
					end if;
				when 4 =>
					Inc_WZ <= '1';
					Set_Addr_To <= aZI;
					Write <= '1';
					if IR(5 downto 4) = "11" then
						Set_BusB_To <= "1001";
					else
						Set_BusB_To(2 downto 1) <= IR(5 downto 4);
						Set_BusB_To(0) <= '0';
						Set_BusB_To(3) <= '0';
					end if;
				when 5 =>
					Write <= '1';
				when others => null;
				end case;
			when "10100000" | "10101000" | "10110000" | "10111000" =>
				-- LDI, LDD, LDIR, LDDR
				MCycles <= "100";
				case to_integer(unsigned(MCycle)) is
				when 1 =>
					Set_Addr_To <= aXY;
					IncDec_16 <= "1100"; -- BC
				when 2 =>
					Set_BusB_To <= "0110";
					Set_BusA_To(2 downto 0) <= "111";
					ALU_Op <= "0000";
					Set_Addr_To <= aDE;
					if IR(3) = '0' then
						IncDec_16 <= "0110"; -- IX
					else
						IncDec_16 <= "1110";
					end if;
				when 3 =>
					I_BT <= '1';
					TStates <= "101";
					Write <= '1';
					if IR(3) = '0' then
						IncDec_16 <= "0101"; -- DE
					else
						IncDec_16 <= "1101";
					end if;
				when 4 =>
					NoRead <= '1';
					TStates <= "101";
				when others => null;
				end case;
			when "10100001" | "10101001" | "10110001" | "10111001" =>
				-- CPI, CPD, CPIR, CPDR
				MCycles <= "100";
				case to_integer(unsigned(MCycle)) is
				when 1 =>
					Set_Addr_To <= aXY;
					IncDec_16 <= "1100"; -- BC
				when 2 =>
					Set_BusB_To <= "0110";
					Set_BusA_To(2 downto 0) <= "111";
					ALU_Op <= "0111";
					Save_ALU <= '1';
					PreserveC <= '1';
					if IR(3) = '0' then
						IncDec_16 <= "0110";
					else
						IncDec_16 <= "1110";
					end if;
				when 3 =>
					NoRead <= '1';
					I_BC <= '1';
					TStates <= "101";
				when 4 =>
					NoRead <= '1';
					TStates <= "101";
				when others => null;
				end case;
			when "01000100"|"01001100"|"01010100"|"01011100"|"01100100"|"01101100"|"01110100"|"01111100" =>
				-- NEG
				Alu_OP <= "0010";
				Set_BusB_To <= "0111";
				Set_BusA_To <= "1010";
				Read_To_Acc <= '1';
				Save_ALU <= '1';
			when "01000110"|"01001110"|"01100110"|"01101110" =>
				-- IM 0
				IMode <= "00";
			when "01010110"|"01110110" =>
				-- IM 1
				IMode <= "01";
			when "01011110"|"01110111" =>
				-- IM 2
				IMode <= "10";
-- 16 bit arithmetic
			when "01001010"|"01011010"|"01101010"|"01111010" =>
				-- ADC HL,ss
				MCycles <= "011";
				case to_integer(unsigned(MCycle)) is
				when 2 =>
					NoRead <= '1';
					ALU_Op <= "0001";
					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";
				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);
						Set_BusB_To(0) <= '0';
					when others =>
						Set_BusB_To <= "1001";
					end case;
				when others =>
				end case;
			when "01000010"|"01010010"|"01100010"|"01110010" =>
				-- SBC HL,ss
				MCycles <= "011";
				case to_integer(unsigned(MCycle)) is
				when 2 =>
					NoRead <= '1';
					ALU_Op <= "0011";
					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";
				when 3 =>
					NoRead <= '1';
					ALU_Op <= "0011";
					Read_To_Reg <= '1';
					Save_ALU <= '1';
					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;
				when others =>
				end case;
			when "01101111" =>
				-- RLD
				MCycles <= "100";
				case to_integer(unsigned(MCycle)) is
				when 2 =>
					NoRead <= '1';
					Set_Addr_To <= aXY;
				when 3 =>
					Read_To_Reg <= '1';
					Set_BusB_To(2 downto 0) <= "110";
					Set_BusA_To(2 downto 0) <= "111";
					ALU_Op <= "1101";
					TStates <= "100";
					Set_Addr_To <= aXY;
					Save_ALU <= '1';
				when 4 =>
					I_RLD <= '1';
					Write <= '1';
				when others =>
				end case;
			when "01100111" =>
				-- RRD
				MCycles <= "100";
				case to_integer(unsigned(MCycle)) is
				when 2 =>
					Set_Addr_To <= aXY;
				when 3 =>
					Read_To_Reg <= '1';
					Set_BusB_To(2 downto 0) <= "110";
					Set_BusA_To(2 downto 0) <= "111";
					ALU_Op <= "1110";
					TStates <= "100";
					Set_Addr_To <= aXY;
					Save_ALU <= '1';
				when 4 =>
					I_RRD <= '1';
					Write <= '1';
				when others =>
				end case;
			when "01000101"|"01001101"|"01010101"|"01011101"|"01100101"|"01101101"|"01110101"|"01111101" =>
				-- RETI, RETN
				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';
				when others => null;
				end case;
			when "01000000"|"01001000"|"01010000"|"01011000"|"01100000"|"01101000"|"01110000"|"01111000" =>
				-- IN r,(C)
				MCycles <= "010";
				case to_integer(unsigned(MCycle)) is
				when 1 =>
					Set_Addr_To <= aBC;
				when 2 =>
					IORQ <= '1';
					if IR(5 downto 3) /= "110" then
						Read_To_Reg <= '1';
						Set_BusA_To(2 downto 0) <= IR(5 downto 3);
					end if;
					I_INRC <= '1';
				when others =>
				end case;
			when "01000001"|"01001001"|"01010001"|"01011001"|"01100001"|"01101001"|"01110001"|"01111001" =>
				-- OUT (C),r
				-- OUT (C),0
				MCycles <= "010";
				case to_integer(unsigned(MCycle)) is
				when 1 =>
					Set_Addr_To <= aBC;
					Set_BusB_To(2 downto 0)	<= IR(5 downto 3);
					if IR(5 downto 3) = "110" then
						Set_BusB_To(3) <= '1';
					end if;
				when 2 =>
					Write <= '1';
					IORQ <= '1';
				when others =>
				end case;
			when "10100010" | "10101010" | "10110010" | "10111010" =>
				-- INI, IND, INIR, INDR
				MCycles <= "100";
				case to_integer(unsigned(MCycle)) is
				when 1 =>
					Set_Addr_To <= aBC;
					Set_BusB_To <= "1010";
					Set_BusA_To <= "0000";
					Read_To_Reg <= '1';
					Save_ALU <= '1';
					ALU_Op <= "0010";
				when 2 =>
					IORQ <= '1';
					Set_BusB_To <= "0110";
					Set_Addr_To <= aXY;
				when 3 =>
					if IR(3) = '0' then
						IncDec_16 <= "0010";
					else
						IncDec_16 <= "1010";
					end if;
					TStates <= "100";
					Write <= '1';
					I_BTR <= '1';
				when 4 =>
					NoRead <= '1';
					TStates <= "101";
				when others => null;
				end case;
			when "10100011" | "10101011" | "10110011" | "10111011" =>
				-- OUTI, OUTD, OTIR, OTDR
				MCycles <= "100";
				case to_integer(unsigned(MCycle)) is
				when 1 =>
					TStates <= "101";
					Set_Addr_To <= aXY;
					Set_BusB_To <= "1010";
					Set_BusA_To <= "0000";
					Read_To_Reg <= '1';
					Save_ALU <= '1';
					ALU_Op <= "0010";
				when 2 =>
					Set_BusB_To <= "0110";
					Set_Addr_To <= aBC;
				when 3 =>
					if IR(3) = '0' then
						IncDec_16 <= "0010";
					else
						IncDec_16 <= "1010";
					end if;
					IORQ <= '1';
					Write <= '1';
					I_BTR <= '1';
				when 4 =>
					NoRead <= '1';
					TStates <= "101";
				when others => null;
				end case;
			end case;

		end case;

		if Mode = 1 then
			if MCycle = "001" then
--				TStates <= "100";
			else
				TStates <= "011";
			end if;
		end if;

		if Mode = 3 then
			if MCycle = "001" then
--				TStates <= "100";
			else
				TStates <= "100";
			end if;
		end if;

		if Mode < 2 then
			if MCycle = "110" then
				Inc_PC <= '1';
				if Mode = 1 then
					Set_Addr_To <= aXY;
					TStates <= "100";
					Set_BusB_To(2 downto 0) <= SSS;
					Set_BusB_To(3) <= '0';
				end if;
				if IRB = "00110110" or IRB = "11001011" then
					Set_Addr_To <= aNone;
				end if;
			end if;
			if MCycle = "111" then
				if Mode = 0 then
					TStates <= "101";
				end if;
				if ISet /= "01" then
					Set_Addr_To <= aXY;
				end if;
				Set_BusB_To(2 downto 0) <= SSS;
				Set_BusB_To(3) <= '0';
				if IRB = "00110110" or ISet = "01" then
					-- LD (HL),n
					Inc_PC <= '1';
				else
					NoRead <= '1';
				end if;
			end if;
		end if;

	end process;

end;