Hi Miguel,

As far as I know, the answer is that you CAN NOT guarantee synchronization
from such a data stream, using just an asynchronous serial transfer method.

However, if you send something more varied that just a string of U's, then
the receiver should resynchronize at some point,because it would encounter
an unexpected bit value for a stop bit, causing a framing error,and making
it wait again until the next start bit.

If you are really dealing with a system in which your line needs to be able
to be connected and disconnected frequently like this, you may need to use
a protocol with better synchronization ability.

Sean


At 10:55 PM 7/25/99 -0300, you wrote:
>Hello all:
>
>I am new in Pic List (three weeks), and new in PIC, and new in uP (and not
>than new in age 8>( ). All of them are very interesting...
>I don't understand all themes because my limited english but the people in
>list seems clever and amusing. Thanks to all by help me to learn more fast.
>
>My question it is probabily a little silly. I beg you your patient with this
>foreing novice...
>
>I am trying to read RS-232 with a PIC (an old topic here), but my problem
>is:
>
>Suppose I just connect my RS-232 reader to a source of signal running before
>I make the connection, and suppose that signal is character "U", ASCII 85,
>Binary 01010101 (N 8 1), how can I recognize Start and Stop bit if data is
>only ....101010101010101010101010....? (I wasn't sure and check in
>Oscilloscope).
>
>That isn't my real problem of course, that make me think on the question of
>sincronizing a signal in a ininterrupted data stream when I connect the
>reader to it. All I have read begin with a long stop bit previous and then,
>the job is counting bits and wait next start bit..
>
>As a matter of fact, my PC clone with W98 Hyperterminal seems unknown the
>technique also, because when I connect RS-232 to GPS data some times send to
>my screen lots of garbage characters: disconnect cable, reconnect and work
>OK (sometimes I have to repeat the procedure a couple of times).
>
>Miguel (Argentina)
>
|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
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