PC to CPU:
  
  'STX' 'ADR' 'P' 'CHK' 'ETX'
      'P'
      
  	  
  	  ASCII-Code 0x50 OR 0x80 = 0xD0
 	    
    
    Example:
    
  	
    ADR = 1
 	  
   
     String =
     
  	
    0x02 0x81 0xD0 0xD1 0x03 (5 Bytes)
 	  
   
 CPU to PC
  
  'STX' 'ADR' 'P' XXX 'CHK' 'ETX' (read value)
      'P'
      
  	  
  	  ASCII-Code 0x50 OR 0x80 = 0xD0
 	    
    
      XXX
      
  	  
  	 actual program number (3 ASCII characters, 001-099) 000 = no program currently running
 	    
    
      Example:
      
  	  
  	  ADR = 1, program 1 runs (HEX 0x30 or HEX 0x80, HEX 0x30 or HEX 0x80, HEX 0x31 or HEX 0x80)
 	    
    
      String =
      
  	  
  	   0x02 0x81 0xD0 0xB0 0xB0 0xB1 0xE0 0x03 (8 Bytes)