pic_ctrl.vhd

一个PIC单片机内核的VHDL实现

            zero_wen <= '1';                   -- Update the ZERO flag.
            IF dest = '0' THEN
                w_wen <= '1';                  -- Store the result in W.      
            ELSE
                file_mwen <= '1';              -- Store the result in the register file.
            END IF;                          
        ELSIF inst(11 DOWNTO 5) = CLRF   THEN
            const_oen <= '1';
            const_01  <= '0';                  -- "0" on the B bus.
            alu_op <= ALUOP_PASSB;             -- Copy B to the output.
            file_mwen <= '1';                  -- Store in the register file.            
            zero_wen <= '1';                   -- Update the ZERO flag.
        ELSIF inst(11 DOWNTO 5) = CLRW   THEN
            const_oen <= '1';
            const_01  <= '0';                  -- "0" on the B bus.
            alu_op <= ALUOP_PASSB;             -- Copy B to the output.
            w_wen <= '1';                      -- Store in W.
            zero_wen <= '1';                   -- Update the ZERO flag.
        ELSIF inst(11 DOWNTO 6) = COMF   THEN
            file_moen <= '1';                  -- FILE on the A bus.
            alu_op <= ALUOP_COM;               -- Invert.
            IF dest = '0' THEN
                w_wen <= '1';                  -- Store the result in W.      
            ELSE
                file_mwen <= '1';              -- Store the result in the register file.
            END IF;                          
            zero_wen <= '1';                   -- Update the ZERO flag.
        ELSIF inst(11 DOWNTO 6) = DECF   THEN
            file_moen <= '1';                  -- FILE on the A bus.
            const_oen <= '1';
            const_01  <= '1';                  -- "1" on the B bus.
            alu_op <= ALUOP_SUB;               -- Subtract.
            IF dest = '0' THEN
                w_wen <= '1';                  -- Store the result in W.      
            ELSE
                file_mwen <= '1';              -- Store the result in the register file.
            END IF;                          
            zero_wen <= '1';                   -- Update the ZERO flag.
        ELSIF inst(11 DOWNTO 6) = DECFSZ THEN
            file_moen <= '1';                  -- FILE on the A bus.
            const_oen <= '1';
            const_01  <= '1';                  -- "1" on the B bus.
            alu_op <= ALUOP_SUB;               -- Perform a substraction.
            IF dest = '0' THEN
                w_wen <= '1';                  -- Store the result in W.      
            ELSE
                file_mwen <= '1';              -- Store the result in the register file.
            END IF;                          
            IF zero = '1' THEN
                inst_skip <= '1';              -- Skip next instruction if result is ZERO.
            END IF;
        ELSIF inst(11 DOWNTO 6) = INCF   THEN
            file_moen <= '1';                  -- FILE on the A bus.
            const_oen <= '1';
            const_01  <= '1';                  -- "1" on the B bus.
            alu_op <= ALUOP_ADD;               -- Add.
            IF dest = '0' THEN
                w_wen <= '1';                  -- Store the result in W.      
            ELSE
                file_mwen <= '1';              -- Store the result in the register file.
            END IF;                          
            zero_wen <= '1';                   -- Update the ZERO flag.
        ELSIF inst(11 DOWNTO 6) = INCFSZ THEN
            file_moen <= '1';                  -- FILE on the A bus.
            const_oen <= '1';
            const_01  <= '1';                  -- "1" on the B bus.
            alu_op <= ALUOP_ADD;               -- Add.
            IF dest = '0' THEN
                w_wen <= '1';                  -- Store the result in W.      
            ELSE
                file_mwen <= '1';              -- Store the result in the register file.
            END IF;                          
            IF zero = '1' THEN
                inst_skip <= '1';              -- Skip next instruction if result is ZERO flag.
            END IF;
        ELSIF inst(11 DOWNTO 6) = IORWF  THEN
            w_b_oen <= '1';                    -- W on the B bus.
            file_moen <= '1';                  -- FILE on the A bus.
            alu_op <= ALUOP_OR;                -- Perform a logical OR.
            zero_wen <= '1';                   -- Update the ZERO flag.
            IF dest = '0' THEN
                w_wen <= '1';                  -- Store the result in W.      
            ELSE
                file_mwen <= '1';              -- Store the result in the register file.
            END IF;                          
        ELSIF inst(11 DOWNTO 6) = MOVF   THEN
            file_moen <= '1';                  -- FILE on the A bus.
            alu_op <= ALUOP_PASSA;             -- Copy A to the output.
            zero_wen <= '1';                   -- Update the ZERO flag.
            IF dest = '0' THEN
                w_wen <= '1';                  -- Store the result in W.      
            ELSE
                file_mwen <= '1';              -- Store the result in the register file.
            END IF;
        ELSIF inst(11 DOWNTO 5) = MOVWF  THEN
            w_a_oen <= '1';                    -- W on the A bus.
            alu_op <= ALUOP_PASSA;             -- Copy A to the output.
            file_mwen <= '1';                  -- Store the result in the register file.
        ELSIF inst(11 DOWNTO 6) = RLF    THEN
            file_moen <= '1';                  -- FILE on the A bus.
            alu_op <= ALUOP_ROL;               -- Shift left.
            carry_wen <= '1';                  -- Update the CARRY flag.
            IF dest = '0' THEN
                w_wen <= '1';                  -- Store the result in W.      
            ELSE
                file_mwen <= '1';              -- Store the result in the register file.
            END IF;
        ELSIF inst(11 DOWNTO 6) = RRF    THEN
            file_moen <= '1';                  -- FILE on the A bus.
            alu_op <= ALUOP_ROR;               -- Shift right.
            carry_wen <= '1';                  -- Update the CARRY flag.
            IF dest = '0' THEN
                w_wen <= '1';                  -- Store the result in W.      
            ELSE
                file_mwen <= '1';              -- Store the result in the register file.
            END IF;
        ELSIF inst(11 DOWNTO 6) = SUBWF  THEN
            w_b_oen <= '1';                    -- W on the B bus.
            file_moen <= '1';                  -- FILE on the A bus.
            alu_op <= ALUOP_SUB;               -- Perform a SUBTRACTION.
            carry_wen <= '1';                  -- Update the CARRY flag.
            zero_wen <= '1';                   -- Update the ZERO flag.
            IF dest = '0' THEN
                w_wen <= '1';                  -- Store the result in W.      
            ELSE
                file_mwen <= '1';              -- Store the result in the register file.
            END IF;                          
        ELSIF inst(11 DOWNTO 6) = SWAPF  THEN
            file_moen <= '1';                  -- FILE on the A bus.
            alu_op <= ALUOP_SWAP;              -- Swap the upper and lower nibbles.
            IF dest = '0' THEN
                w_wen <= '1';                  -- Store the result in W.      
            ELSE
                file_mwen <= '1';              -- Store the result in the register file.
            END IF;
        ELSIF inst(11 DOWNTO 6) = XORWF  THEN
            w_b_oen <= '1';                    -- W on the B bus.
            file_moen <= '1';                  -- FILE on the A bus.
            alu_op <= ALUOP_XOR;               -- Perform a logical XOR.
            zero_wen <= '1';                   -- Update the ZERO flag.
            IF dest = '0' THEN
                w_wen <= '1';                  -- Store the result in W.      
            ELSE
                file_mwen <= '1';              -- Store the result in the register file.
            END IF;                          
        ELSIF inst(11 DOWNTO 8) = BCF    THEN
            file_moen <= '1';                  -- FILE on the A bus.
            imm_oen <= '1';                    -- IMMEDIATE on the B bus.
            alu_op <= ALUOP_BITCLR;            -- Bit clear.
            file_mwen <= '1';                  -- Store the result in the register file.
        ELSIF inst(11 DOWNTO 8) = BSF    THEN
            file_moen <= '1';                  -- FILE on the A bus.
            imm_oen <= '1';                    -- IMMEDIATE on the B bus.
            alu_op <= ALUOP_BITSET;            -- Bit set.
            file_mwen <= '1';                  -- Store the result in the register file.
        ELSIF inst(11 DOWNTO 8) = BTFSC  THEN
            file_moen <= '1';                  -- FILE on the A bus.
            imm_oen <= '1';                    -- IMMEDIATE on the B bus.
            alu_op <= ALUOP_BITTESTCLR;        -- Test if the bit is clear.
            IF zero = '1' THEN
                inst_skip <= '1';              -- Skip next instruction if bit is clear.
            END IF;
        ELSIF inst(11 DOWNTO 8) = BTFSS  THEN
            file_moen <= '1';                  -- FILE on the A bus.
            imm_oen <= '1';                    -- IMMEDIATE on the B bus.
            alu_op <= ALUOP_BITTESTSET;        -- Test if the bit is set.
            IF zero = '1' THEN
                inst_skip <= '1';              -- Skip next instruction if bit is set.
            END IF;
        ELSIF inst(11 DOWNTO 8) = ANDLW  THEN
            w_a_oen <= '1';                    -- W on the A bus.
            imm_oen <= '1';                    -- IMMEDIATE on the B bus.
            alu_op <= ALUOP_AND;               -- Perform a logical AND.
            zero_wen <= '1';                   -- Update the ZERO flag.
            w_wen <= '1';                      -- Store the result in W.      
        ELSIF inst(11 DOWNTO 8) = IORLW  THEN
            w_a_oen <= '1';                    -- W on the A bus.
            imm_oen <= '1';                    -- IMMEDIATE on the B bus.
            alu_op <= ALUOP_OR;                -- Perform a logical OR.
            zero_wen <= '1';                   -- Update the ZERO flag.
            w_wen <= '1';                      -- Store the result in W.      
        ELSIF inst(11 DOWNTO 8) = XORLW  THEN
            w_a_oen <= '1';                    -- W on the A bus.
            imm_oen <= '1';                    -- IMMEDIATE on the B bus.
            alu_op <= ALUOP_XOR;               -- Perform a logical XOR.
            zero_wen <= '1';                   -- Update the ZERO flag.
            w_wen <= '1';                      -- Store the result in W.      
        ELSIF inst(11 DOWNTO 8) = MOVLW  THEN
            imm_oen <= '1';                    -- IMMEDIATE on the B bus.
            alu_op <= ALUOP_PASSB;             -- Copy B to the output.
            w_wen <= '1';                      -- Store the result in W.      
        ELSIF inst(11 DOWNTO 9) = GOTO   THEN
            pc_load <= '1';
            inst_skip <= '1';                  -- Force a NOP in the instruction register.
        ELSIF inst(11 DOWNTO 8) = CALL   THEN
            imm_oen <= '1';                    -- IMMEDIATE on the B bus.
            alu_op <= ALUOP_PASSB;             -- Copy B to the output.
            pc_push <= '1';                    -- Push the PC on the stack & load new value.
            inst_skip <= '1';                  -- Force a NOP in the instruction register.
        ELSIF inst(11 DOWNTO 8) = RETLW  THEN
            pc_pop <= '1';                     -- Pop the PC from the stack.
            imm_oen <= '1';                    -- IMMEDIATE on the B bus.
            alu_op <= ALUOP_PASSB;             -- Copy B to the output.
            w_wen <= '1';                      -- Store the result in W.      
            inst_skip <= '1';                  -- Force a NOP in the instruction register.
        ELSIF inst(11 DOWNTO 2) = TRIS   THEN
            w_a_oen <= '1';                    -- W on the A bus.
            alu_op <= ALUOP_PASSA;             -- Copy A to the output.
            CASE tris_sel IS
              WHEN "01" => tris_a_wen <= '1';  -- Store in the appropriate TRIS register.
              WHEN "10" => tris_b_wen <= '1';
              WHEN "11" => tris_c_wen <= '1';
              WHEN OTHERS => NULL;
            END CASE;
        ELSIF inst(11 DOWNTO 0) = OPTION THEN
        -- Not implemented.
        ELSIF inst(11 DOWNTO 0) = SLEEP  THEN
        -- Not implemented.
        ELSIF inst(11 DOWNTO 0) = CLRWDT THEN
        -- Not implemented.
        END IF;
    END PROCESS;
END mixed;