Try it like this.

Code:
'pic18f6722
osc 40
arraysize  con  20
djam      con     %01110111
ack       con     $06 
command   var     byte[20]
message   var     byte[20]

loop1:
  Arraywrite message,[hex ack," ",bin djam,0]
  debug str message,10,13                                                     
  arraywrite message,[rep 0\arraysize]
  pause 1000
goto loop1