Products Mentioned

ADV7802 Production
The ADV7802 is a high quality, single-chip, multiformat 3D comb filter, video decoder, and graphics digitizer. This multiformat 3D comb filter decoder...
Datasheet
ADV7802 on Analog.com

Thread Details

  • State Verified Answer
  • Replies 3 replies
  • Subscribers 80 subscribers
  • Views 473 views
  • Users 0 members are here
Options
 
Related Content

        

            Post
             Go back to editing
        

    

    


    

    









		


















	
	
			
	
			
		
	
	
		

	    
	    
	    		
How to use the undocumented "DIGITAL CVBS INPUT" from the ADV7802

		
	
				

			

									
					    vrunk11
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Apr 12, 2025 
				
			
			
		
    
		
		                    	    
    
        	    
    Thread Summary
    
                The user is designing a board using the ADV7802 chip and wants to use the digital CVBS input mode. The final answer suggests that a hidden MUX or undocumented register can select the CVBS decoder's input source as digital (12-bit parallel) over D[11:0], clocked at 28.63636 MHz. For early design, it's recommended to route D[11:0] and CLKIN, and add a test header or mux to toggle between analog and digital CVBS paths. The accompanying answers clarify that there are no specific registers for this mode and suggest connecting the MCU/FPGA to CLKIN(78) for testing.
                        	    
    
                
                     AI Generated Content
                
    	    
    
             
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Datasheet/Specs
    
    		        		            		    
    Product Number:  ADV7802  
    
    		        		    		    
    
		    		    
		    			
    
			    
    Hello , I'm an independent developer working on designing a board using your ADV7802 chip.

    By looking at the internal diagram, I can see that the digital input are muxed at the same place as the digital output of the different 12bit ADC.
    

    i also noticed in the datasheet that there is a mention of a "digital cvbs input mode" on the pin 78 (CLKIN).

    It turns out I'm part of a project where I work with digital cvbs file. So i would love if i could use an mcu or an fpga to feed my digital cvbs to the chip so i could leverage his 3D decoder and 3D NR without going to analogue.

    Could you guide me on how i could achieve this goal and how i could use that digital cvbs input mode.

    I would really appreciate your help, thanks.
    
			
    
			
									
		                             
                        

    
    
                                            
                 Video Products
                
                                                    
                 adv7802
                
                                                    
                 Datasheet/Specs
                
                                                    
                 hardware
                
                                                    
                 Data Path Management
                
                                        
                                            
                
                
                                
                    Show More
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

    • 
	
      



	
		
	
	



      
	
      
		
      
							
					
      
		
      
		    
		    		    
			
				
									
							        
			
			
			
      •  Analog Employees  
      •  Super User  
      
            
						
                            
            
            				
            
                on Apr 15, 2025 7:47 AM
            
            
						
			            		
      
		
										0
					
	
      

		
		
      
		
      
                                
                                                            
      
					
      Hi,
      

        Kindly note that, There is no register which is available for 'digital cvbs input mode' so just connect your MCU/FPGA  with CLKIN(78) pin and let us know.
      

      

      Thanks,
      

      Poornima
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

      • 

	

    • 
	
      



	
		
	
	



      
	
      
		
      
							
					
      
		
      
		    
		    		    
			
				
									
							        
			
			
			
        
            
						
                            
            
            				
            
                on Apr 19, 2025 5:30 AM
            
            
												
						in reply to PoornimaSubramani
					
										
			            		
        
		
										0
					
	
        

		
		
        
		
        
                                
                                                            
        
					
        the CLKIN jusst mention it could be used with the digital cvbs input mode but doesn't say it is an input.
        

         
        

        i supose there is a way to use some reserved register to mux the digital cvbs to the CVBS processing core. but i would also have to know the exact format used by the decoder and how to let it accept 12 bit data on the digital input. i'm also in the design phase, so i can't test without knowing how that should be implemented. I suppose the digital cvbs input must have been used during the design phase to test the comb filter but as then be left undocumented other that that mention on the screenshot.
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

        • 

	

      • 
	
        



	
			
		
	



        
	
        
		
        
							
					
        
		
        
		    
		    		    
			
				
									
							        
			
			
			
        •  Analog Employees  
        •  Super User  
        
            
						
                            
            
            				
            
                on Apr 21, 2025 7:29 AM
            
            
												
						in reply to vrunk11
					
										
			            		
        
		
										0
					
	
        

		
		
        
		
        
                                
                                                            
        
					
        Hi,
        

        Kindly note that, We don't any register details other than what available in the manuals.
        

        A hidden MUX or undocumented register selects the CVBS decoder’s input source as digital (parallel) instead of analog So i believe, We can make it by giving 12-bit digital CVBS over digital input interface D[11:0].
        

        If you're in early design:
        Leave flexibility in your layout (route D[11:0] and CLKIN).
        Add a test header or mux to toggle between analog and digital CVBS paths.
        Design assuming 12-bit CVBS over D[11:0], clocked at 28.63636 MHz (as per XTAL).
        

        

        

        Thanks,
        

        Poornima
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
						
						
				
				
		
		
        
			
		
        
	
        

        

        •