ds18b20_.vhd

自己写的一个测温元件（ds18b20）的驱动程序

                    S_State<=T_Write0;                                                         
                 else                                                                          
                    S_State<=T_Write1;                                                         
                 end if;                                                                       
                 V_WR_BitCNT := V_WR_BitCNT+1;                                                 
            when 8 =>                                                                          
                 if (V_WRByteCNT=0) then     -- 第一次写0XCC完毕                               
                    S_State<=T_CMD_44;                                                         
                    V_WRByteCNT:=1;                                                            
                 elsif (V_WRByteCNT=1) then  -- 写0X44完毕                                     
                    S_State<=T_ConvWait;     -- 等待转换完成                                   
                    V_WRByteCNT:=2;                                                            
                 elsif (V_WRByteCNT=2) then  --第二次写0XCC完毕                                
                    S_State<=T_CMD_BE;                                                         
                    V_WRByteCNT:=3;                                                            
                 elsif (V_WRByteCNT=3) then  -- 写0XBE完毕                                     
                    S_State<=T_GetTemp;                                                        
                    V_WRByteCNT:=0; 
                 else
                    V_WRByteCNT:=0;                                                            
                 end if;                                                                       
                 V_WR_BitCNT := 0; 
            when others =>
                 V_WR_BitCNT := 0;                                                             
            end case;                                                                          
        when T_Write0=>                                                                        
            case V_Write0_CNT is                                                               
            when 0=>                                                                           
               P_dq<='0';                                                                      
               if (V_Counter>=78) then                                                         
                  V_Counter := 0;                                                              
                  V_Write0_CNT:=1;                                                             
               else                                                                            
                  V_Counter := V_Counter+1;                                                    
               end if;                                                                         
            when 1=>                                                                           
               P_dq<='Z';                                                                      
               if (V_Counter>=2) then                                                          
                  V_Counter := 0;                                                              
                  V_Write0_CNT:=2;                                                             
               else                                                                            
                  V_Counter := V_Counter+1;                                                    
               end if;                                                                         
            when 2=>                                                                           
               S_State<=T_WriteByte;                                                           
               V_Write0_CNT:=0;                                                                
            when others=>V_Write0_CNT:=0;                                                      
            end case;                                                                          
        when T_Write1=>                                                                        
            case V_Write1_CNT is                                                               
            when 0=>                                                                           
               P_dq<='0';                                                                      
               if (V_Counter=8) then                                                           
                  V_Counter := 0;                                                              
                  V_Write1_CNT:=1;                                                             
               else                                                                            
                  V_Counter := V_Counter+1;                                                    
               end if;                                                                         
            when 1=>                                                                           
               P_dq<='Z';                                                                      
               if (V_Counter=72) then                                                          
                  V_Counter := 0;                                                              
                  V_Write1_CNT:=2;                                                             
               else                                                                            
                  V_Counter := V_Counter+1;                                                    
               end if;                                                                         
            when 2=>                                                                           
               S_State<=T_WriteByte;                                                           
               V_Write1_CNT:=0;                                                                
            when others=>
               V_Write1_CNT:=0;                                                                
           end case;                                                                           
        when T_GetTemp=>              -- 好像只接受了12位                                      
              case V_RD_BitCNT is                                                              
              when 0 to 11=>                                                                   
                  S_State<=T_Read_Bit;                                                         
                  V_ReadTemp(V_RD_BitCNT):=S_RD_Bit;                                            
                  V_RD_BitCNT:=V_RD_BitCNT+1;                                                  
              when 12=>     
                  P_RD_Temp <= V_ReadTemp;                                                      
                  V_RD_BitCNT:=0;                                                              
                  S_State<=T_DS_Rest; 
              when others => 
                  V_RD_BitCNT:=0;                                                              
              end case;
        when T_Read_Bit=>                                                                      
            case V_DS_Read_st is                                                               
            when 0=>                                                                           
               P_dq<='0';                                                                      
               if (V_Counter=4) then                                                           
                  V_DS_Read_st:=1;                                                             
                  V_Counter := 0;                                                              
               else                                                                            
                  V_Counter := V_Counter+1;                                                    
               end if;                                                                         
            when 1=>                                                                           
               P_dq<='Z';                                                                      
               if (V_Counter>4) then                                                           
                  V_DS_Read_st:=2;                                                             
                  V_Counter := 0;                                                              
               else                                                                            
                  V_Counter := V_Counter+1;                                                    
               end if;                                                                         
            when 2=>                                                                           
               S_RD_Bit<=P_dq;  
               V_DS_Read_st:=3;                                                                
            when 3=>                                                                           
               if (V_Counter=45) then                                                          
                  V_Counter := 0;                                                              
                  V_DS_Read_st:=0;                                                             
                  S_State<=T_GetTemp;                                                          
               else                                                                            
                  V_Counter := V_Counter+1;                                                    
               end if;                                                                         
            when others=>V_DS_Read_st:=0;                                                      
            end case;                                                                          
        when T_DS_Rest=> 
              if V_ms_Counter = 100 then   -- 休息100ms
                 S_State<=T_Reset_st;
                 V_ms_Counter := 0;
              else                                                                             
                  if V_Counter>=1000 then                                                      
                     V_ms_Counter := V_ms_Counter+1;                                             
                     V_Counter := 0;                                                           
                  else                                                                         
                     V_Counter := V_Counter+1;                                                 
                  end if;                                                                      
              end if;                                                                          
       when others => 
              S_State <= T_Reset_st;
              V_Counter := 0;                                          
       end case;                                                                               
   end if;    
end if;                                                                                 
end process;                                                                                   
end Behavioral;