cannot find the reason for such a strange behavior

[richard]

I did it this once for you , problem is definitely elsewhere

and

DMY = W0//256
Pulse[75] = (255 - DMY)

can be simplified to

Pulse[75] =~w0

#CONFIG
             __config        _CONFIG1,    _FOSC_INTOSC & _CP_OFF & _WDTE_ON  &  _PWRTE_ON  &  _MCLRE_ON  & _CLKOUTEN_OFF
              __config      _CONFIG2, _PLLEN_ON & _LVP_OFF
#ENDCONFIG

  



DEFINE OSC 32

    OSCCON=$70
   ANSELA=0
   ANSELC=0
  
   
   
   TRISA = %111110
   TRISC = %11111111        ' set PORTC I/O
 


 j var byte
 k var word
 l var byte
 pulse var byte[76]
 decode var byte[4]
 w0 var word
 dmy var byte
 
 
 
  
    DEFINE DEBUG_REG PORTA
    DEFINE DEBUG_BIT 0      ;  if not used for pwr  
    DEFINE DEBUG_BAUD 9600
    DEFINE DEBUG_MODE 0     
    pause 2000
    Debug "Start",13 ,10      
 
 
 
 
 
 
 
 
 
 
  main:
 


    gosub XBee_Value
    
    
    Pulse[0] = "1"
    Pulse[1] = "5"
    Pulse[2] = "0"
    Pulse[3] = " "
    Pulse[4] = "A"
    Pulse[5] = "0"
    Pulse[6] = "="
    Pulse[7] = Decode[3]
    Pulse[8] = Decode[2]
    Pulse[9] = Decode[1]
    Pulse[10] = Decode[0]
    
    
'    CIndex = 1
    gosub XBee_Value
    
    
    Pulse[11] = " "
    Pulse[12] = "A"
    Pulse[13] = "1"
    Pulse[14] = "="
    Pulse[15] = Decode[3]
    Pulse[16] = Decode[2]
    Pulse[17] = Decode[1]
    Pulse[18] = Decode[0]
    
    
    
    
'    CIndex = 2
    gosub XBee_Value
    
    
    Pulse[19] = " "
    Pulse[20] = "A"
    Pulse[21] = "2"
    Pulse[22] = "="
    Pulse[23] = Decode[3]
    Pulse[24] = Decode[2]
    Pulse[25] = Decode[1]
    Pulse[26] = Decode[0]
    
    
    '------------------
'    CIndex = 3
    gosub XBee_Value
    
    
    Pulse[27] = " "
    Pulse[28] = "A"
    Pulse[29] = "3"
    Pulse[30] = "="
    Pulse[31] = Decode[3]
    Pulse[32] = Decode[2]
    Pulse[33] = Decode[1]
    Pulse[34] = Decode[0]
    
    
'    CIndex = 4
    gosub XBee_Value
    
    
    Pulse[35] = " "
    Pulse[36] = "A"
    Pulse[37] = "4"
    Pulse[38] = "="
    Pulse[39] = Decode[3]
    Pulse[40] = Decode[2]
    Pulse[41] = Decode[1]
    Pulse[42] = Decode[0]
    
    
    
    
'    CIndex = 5
    gosub XBee_Value
    
    
    Pulse[43] = " "
    Pulse[44] = "A"
    Pulse[45] = "5"
    Pulse[46] = "="
    Pulse[47] = Decode[3]
    Pulse[48] = Decode[2]
    Pulse[49] = Decode[1]
    Pulse[50] = Decode[0]
    '------------------
'    CIndex = 6
    gosub XBee_Value
    
    
    Pulse[51] = " "
    Pulse[52] = "A"
    Pulse[53] = "6"
    Pulse[54] = "="
    Pulse[55] = Decode[3]
    Pulse[56] = Decode[2]
    Pulse[57] = Decode[1]
    Pulse[58] = Decode[0]
    
    
'    CIndex = 7
    gosub XBee_Value
    
    
    Pulse[59] = " "
    Pulse[60] = "A"
    Pulse[61] = "7"
    Pulse[62] = "="
    Pulse[63] = Decode[3]
    Pulse[64] = Decode[2]
    Pulse[65] = Decode[1]
    Pulse[66] = Decode[0]
    
    
    
    
'    CIndex = 8
    gosub XBee_Value
    
    
    Pulse[67] = " "
    Pulse[68] = "A"
    Pulse[69] = "8"
    Pulse[70] = "="
    Pulse[71] = Decode[3]
    Pulse[72] = Decode[2]
    Pulse[73] = Decode[1]
    Pulse[74] = Decode[0]
    
    
    '------------------ Start CRC Function
    W0 = 0
    For DMY = 0 To 74
    W0 = W0 + Pulse[DMY]
    next DMY
    DMY = W0//256      ;  why  ?
    Pulse[75] = (255 - DMY) ;  why   ?
    ;  this line could replace the above two lines  ie   Pulse[75]=~w0
    l=~w0  ;debug    proof of above
    j=w0   ;debug
    
    ' -------------------- End CRC function
    
    Debug 13 ,10 ,#w0,9,#dmy,9,#j ,9,#Pulse[75],9 ,#l
    pause 1000 
 goto main  
    

 XBee_Value:
 for j=0 to 3
   random k
  Decode[j]=k
 next
 return