IC_XRL_D_DATA     when s_command             = XRL_D_DATA     else    IC_NOP;  -------------------------------------------------------------------------------- purpose: main-process to control the mcu--          includes the interupt-handling and the state machine-- inputs:  state,s_help,s_ti,s_ri,s_it0,s_ie0,s_it1,s_ie1,s_tf0,s_tf1,--          s_bit_data,aludata_i,s_command,s_inthigh,--          s_intlow,acc,psw,s_intpre,s_intpre2,ie,ip-- outputs: pc_inc_en_o,s_nextstate_o,adr_mux_o,data_mux_o,bdata_mux_o--          regs_wr_en_o,help_en_o,help16_en_o,helpb_en_o,inthigh_en_o--          intlow_en_o,intpre2_en_o,inthigh_d_o,intlow_d_o,intpre2_d_o------------------------------------------------------------------------------ p_state: process (state,s_help,s_ti,s_ri,s_it0,s_ie0,s_it1,s_ie1,s_tf0,s_tf1,                   s_bit_data,aludata_i,s_instr_category,s_inthigh,                   s_intlow,acc,psw,s_intpre,s_intpre2,ie,ip)  begin    s_data_mux   <= "0000";             -- default values    s_adr_mux    <= "0000";    s_bdata_mux  <= "0000";    alu_cmd_o    <= OFF;    s_regs_wr_en <= "000";    s_help_en    <= "0000";    s_help16_en  <= "00";    s_helpb_en   <= '0';    s_pc_inc_en  <= "0000";    s_inthigh_en <= '0';    s_intlow_en  <= '0';    s_intpre2_en <= '0';    s_inthigh_d  <= '0';    s_intlow_d   <= '0';    s_intpre2_d  <= '0';    s_adrx_mux   <= "00";    s_wrx_mux    <= '0';    s_nextstate  <= FETCH;    if state=STARTUP then      -- Power up wait cycle      NULL;    else      -- begin of starting the interrupt procedure                                                      -- saving the old adress      if (s_intpre='1' and state=FETCH) or s_intpre2='1' then        if state=FETCH then          s_intpre2_en <= '1';          s_intpre2_d <= '1';          s_regs_wr_en <= "001";            -- increment stackpointer          s_nextstate <= EXEC1;        elsif state=EXEC1 then          if (PX0 and EX0 and s_ie0)='1' then   -- external interrupt 0            s_help_en <= "0101";                -- interruptvector 0003h            s_inthigh_d <= '1';            s_inthigh_en <= '1';            if s_it0='1' then         -- interrupt is edge-sensitive              s_adr_mux <= "0001";              s_regs_wr_en <= "110";  -- reset IE0            else              NULL;            end if;          elsif (PT0 and ET0 and s_tf0)='1' then  -- timer interrupt 0            s_help_en <= "0110";                  -- interruptvector 000Bh            s_inthigh_d <= '1';            s_inthigh_en <= '1';            s_adr_mux <= "0010";            s_regs_wr_en <= "110";                -- reset TF0          elsif (PX1 and EX1 and s_ie1)='1' then  -- external interrupt 1            s_help_en <= "0111";                  -- interruptvector 0013h            s_inthigh_d <= '1';            s_inthigh_en <= '1';            if s_it1='1' then         -- interrupt is edge-sensitive              s_adr_mux <= "0011";              s_regs_wr_en <= "110";  -- reset IE1            else              NULL;            end if;          elsif (PT1 and ET1 and s_tf1)='1' then  -- timer interrupt 1            s_help_en <= "1000";                  -- interruptvector 001Bh            s_inthigh_d <= '1';            s_inthigh_en <= '1';            s_adr_mux <= "0100";            s_regs_wr_en <= "110";          -- reset TF1          elsif (PS0 and ES and (s_ri or s_ti))='1' then -- serial interrupt 0            s_help_en <= "1001";            -- interruptvector 0023h            s_inthigh_d <= '1';            s_inthigh_en <= '1';         elsif (EX0 and s_ie0)='1' then   -- external interrupt 0 low priority            s_help_en <= "0101";          -- interruptvector 0003h            s_intlow_d <= '1';            s_intlow_en <= '1';            if s_it0='1' then         -- interrupt is edge-sensitive              s_adr_mux <= "0001";              s_regs_wr_en <= "110";  -- reset IE0            else              NULL;            end if;          elsif (ET0 and s_tf0)='1' then   -- timer interrupt 0 low priority            s_help_en <= "0110";           -- interruptvector 000Bh            s_intlow_d <= '1';            s_intlow_en <= '1';            s_adr_mux <= "0010";            s_regs_wr_en <= "110";         -- reset TF0          elsif (EX1 and s_ie1)='1' then   -- external interrupt 1 low priority            s_help_en <= "0111";           -- interruptvector 0013h            s_intlow_d <= '1';            s_intlow_en <= '1';            if s_it0='1' then         -- interrupt is edge-sensitive              s_adr_mux <= "0011";              s_regs_wr_en <= "110";  -- reset IE1            else              NULL;            end if;          elsif (ET1 and s_tf1)='1' then   -- timer interrupt 1 low priority            s_help_en <= "1000";           -- interruptvector 001Bh            s_intlow_d <= '1';            s_intlow_en <= '1';            s_adr_mux <= "0100";            s_regs_wr_en <= "110";               -- reset TF1          elsif (ES and (s_ri or s_ti))='1' then -- serial int 0 low priority            s_help_en <= "1001";                 -- interruptvector 0023h            s_intlow_d <= '1';            s_intlow_en <= '1';          else            NULL;          end if;          s_nextstate <= EXEC2;        elsif state=EXEC2 then          s_adr_mux <= "0101";          s_data_mux <= "0001";         -- data = pc(7 downto 0)          s_regs_wr_en <= "101";        -- write one byte and increment SP          s_nextstate <= EXEC3;        elsif state=EXEC3 then          s_intpre2_d <= '0';          s_intpre2_en <= '1';          s_adr_mux <= "0101";          s_data_mux <= "0010";         -- data = pc(15 downto 8)          s_regs_wr_en <= "100";        -- write one byte          s_pc_inc_en <= "0011";        -- load program counter          s_nextstate <= FETCH;        else          s_nextstate <= FETCH;        end if;       -- end of starting interrupt procedure       else        case s_instr_category is          ---------------------------------------------------------------------          when IC_ACALL =>              -- ACALL addr11            if state=FETCH then              s_adr_mux <= "1111";      -- adress = sp + 1              s_data_mux <= "1110";     -- data = (pc+2)(7 downto 0)              s_regs_wr_en <= "101";    -- write one byte and increment SP              s_help16_en <= "10";      -- s_help16 = pc+2              s_pc_inc_en <= "0001";    -- increment program-counter              s_nextstate <= EXEC1;            elsif state=EXEC1 then              s_adr_mux <= "1111";       -- adress = sp + 1              s_data_mux <= "1101";      -- data = s_help16(15 downto 8)              s_regs_wr_en <= "101";     -- write one byte and increment SP              s_pc_inc_en <= "0100";     -- load PC with 11 bits (2k block)              s_nextstate <= FETCH;            end if;          ---------------------------------------------------------------------          when IC_ADD_A_RR =>           -- ADD A,Rr            if state=FETCH then              s_adr_mux <= "0110";      -- adress = RR-adress              s_nextstate <= EXEC1;            elsif state=EXEC1 then              alu_cmd_o <= ADD_ACC_RAM; -- addition command (ACC + RAM_DATA)              s_data_mux <= "0011";     -- data = aludata_i              s_regs_wr_en <= "011";    -- write ACC and CY,OV,AC              s_pc_inc_en <= "0001";    -- increment program-counter              s_nextstate <= FETCH;            end if;          ---------------------------------------------------------------------          when IC_ADD_A_D =>            -- ADD A, direct            if state=FETCH then              s_pc_inc_en <= "0001";    -- increment program-counter              s_nextstate <= EXEC1;            elsif state=EXEC1 then              s_adr_mux <= "1000";      -- adress = rom_data_i              s_nextstate <= EXEC2;            elsif state=EXEC2 then              alu_cmd_o <= ADD_ACC_RAM; -- addition command (ACC + RAM_DATA)              s_data_mux <= "0011";     -- data = aludata_i              s_regs_wr_en <= "011";    -- write ACC and CY,OV,AC              s_pc_inc_en <= "0001";    -- increment program-counter              s_nextstate <= FETCH;            end if;          ---------------------------------------------------------------------          when IC_ADD_A_ATRI =>         -- ADD A,@Ri            if state=FETCH then              s_adr_mux <= "0111";      -- address = Ri-register              s_nextstate <= EXEC1;            elsif state=EXEC1 then              alu_cmd_o <= ADD_ACC_RAM; -- addition command (ACC + RAM_DATA)              s_data_mux <= "0011";     -- data = aludata_i              s_regs_wr_en <= "011";    -- write ACC and CY,OV,AC              s_pc_inc_en <= "0001";    -- increment program-counter              s_nextstate <= FETCH;            end if;          ---------------------------------------------------------------------          when IC_ADD_A_DATA =>         -- ADD A, DATA            if state=FETCH then              s_pc_inc_en <= "0001";    -- increment program-counter              s_nextstate <= EXEC1;            elsif state=EXEC1 then              alu_cmd_o <= ADD_ACC_ROM; -- addition command (ACC + ROM_DATA_I)              s_data_mux <= "0011";     -- data = aludata_i              s_regs_wr_en <= "011";    -- write ACC and CY,OV,AC              s_pc_inc_en <= "0001";    -- increment program-counter              s_nextstate <= FETCH;            end if;          ---------------------------------------------------------------------          when IC_ADDC_A_RR =>          -- ADDC A,Rr            if state=FETCH then              s_adr_mux <= "0110";      -- adress = RR-adress              s_nextstate <= EXEC1;            elsif state=EXEC1 then              alu_cmd_o <= ADDC_ACC_RAM;  -- addition command (ACC+RAM_DATA+CY)              s_data_mux <= "0011";       -- data = aludata_i              s_regs_wr_en <= "011";      -- write ACC and CY,OV,AC              s_pc_inc_en <= "0001";      -- increment program-counter              s_nextstate <= FETCH;            end if;          ---------------------------------------------------------------------          when IC_ADDC_A_D =>           -- ADDC A, direct            if state=FETCH then              s_pc_inc_en <= "0001";    -- increment program-counter              s_nextstate <= EXEC1;            elsif state=EXEC1 then              s_adr_mux <= "1000";      -- adress = rom_data_i              s_nextstate <= EXEC2;            elsif state=EXEC2 then              alu_cmd_o <= ADDC_ACC_RAM;  -- addition command (ACC+RAM_DATA+CY)              s_data_mux <= "0011";       -- data = aludata_i              s_regs_wr_en <= "011";      -- write ACC and CY,OV,AC              s_pc_inc_en <= "0001";      -- increment program-counter              s_nextstate <= FETCH;            end if;          ---------------------------------------------------------------------          when IC_ADDC_A_ATRI =>        -- ADDC A,@Ri            if state=FETCH then              s_adr_mux <= "0111";      -- address = Ri-register              s_nextstate <= EXEC1;            elsif state=EXEC1 then              alu_cmd_o <= ADDC_ACC_RAM;  -- addition command (ACC+RAM_DATA+CY)              s_data_mux <= "0011";       -- data = aludata_i              s_regs_wr_en <= "011";      -- write ACC and CY,OV,AC              s_pc_inc_en <= "0001";      -- increment program-counter              s_nextstate <= FETCH;            end if;          ---------------------------------------------------------------------          when IC_ADDC_A_DATA =>        -- ADDC A, data            if state=FETCH then              s_pc_inc_en <= "0001";    -- increment program-counter