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No-OS SW Reference design(AD9361) for Zedboard+AD-FMCOMMS2

		
	
				

			

									
					    angleIsDancing
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jan 13, 2016 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
		    			
    
			    
    Hi,all:
    
 
           I got the No-OS SW reference design from website. in the function adc_capture() of "adc_core.c" file.
    
 
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     adc_dma_read(AXI_DMAC_REG_IRQ_PENDING, &reg_val);
    
    
    
    
     
     adc_dma_write(AXI_DMAC_REG_IRQ_PENDING, reg_val);
    
    
       
  
    
 
    
 
    ==========================================
    
 
    my question is:
    
 
         why it reads value from register into reg_val and then immediately write reg_val to register. 
    
 
    is register value  always equal to reg_val before reg_val written back to the register? if yes,why reg_val needs to be written back to the register.  if no, in what cases they are different. 
    
 
    thanks,
    
 
    gan
    
			
    
			
									
		                             
                        
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			








	
	
	
	



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                on Jan 19, 2016 6:11 AM
            
            
						
			            		
        
		
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        Hi Dragos,
        
 
        Thank you for your reply, I am still confused. 
        
 
        Since the bits which are set are already 0x01, why we still need the code(adc_dma_write(AXI_DMAC_REG_IRQ_PENDING, reg_val) to set them to 0x01?
        
 
        and why do you mean by “write 0x01 to clear a specific bit from the AXI_DMAC_REG_IRQ_PENDING register.”?
        
 
        yours,
        
 
        gan
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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                on Jan 19, 2016 6:11 AM
            
            
						
			            		
          
		
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          Hi Dragos,
          
 
          Thank you for your reply, I am still confused. 
          
 
          Since the bits which are set are already 0x01, why we still need the code(adc_dma_write(AXI_DMAC_REG_IRQ_PENDING, reg_val) to set them to 0x01?
          
 
          and why do you mean by “write 0x01 to clear a specific bit from the AXI_DMAC_REG_IRQ_PENDING register.”?
          
 
          yours,
          
 
          gan
          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
						
				
				
		
		
          
			
		
          
	
          

          

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