process hung problem + self reset

[eng.alamin]

hello no (interrupts)
this is my code
no schematic release yet still prototypal
but u can figer it out from code

pin b.0 is serail in
pin a.3 is audio out

 define osc 20
   Include "modedefs.bas"
 
 TRISA = %00000000
  gdata var byte[21]

  x var byte 
  ok var bit
 main:
 x = 0
 
    gps:
        if ok == 0 then 
  serin2 portb.0 , 188 ,[wait("GPS") , str gdata\20]
         toggle portb.1
     dtmfout porta.3 ,100 ,100,[ 10 , 0 , 10 ]
             
             
     for x = 0 to 20
                   pause 10
                 if  gdata[x] = "." then
                    gdata[x] = 12
                    endif
                      dtmfout porta.3 ,100,100,[ gdata[x]  ]  
                       
  next x  
    ok = 1
    endif
  
   serin2 portb.0 , 188 ,[wait("SD") , str gdata\4]
   ok = 0
        toggle portb.2
     dtmfout porta.3 ,100,100,[ 10 , 1 , 10 ]
             pause 1
           
     for x = 0 to 4
                     pause 10
                 if  gdata[x] = "." then
                    gdata[x] = 12
                    endif
                    dtmfout porta.3 ,100,100,[ gdata[x]  ]  
                       
  next x      
  pause 50           
 goto main