Ops!!! I discovery an error...the correct time to 1 bit is 1/4800 ~ 208us! I was using 21us (20.83us was wrong) on char_pacing. Sorry by primary error!
However I will test only on next week, then I would like to know with more detail if my program using the correct value of char_pacing (208us) is rigth to generate a second stop bit, and if is necessary to enable the pull-up, because the data is passed em TTL levels.
Thanks

Pimentel