From OpenSCADAWiki
Notes
Communications via the serial interfaces have a number of features. The most important feature is the criterion for the end of the message and the waiting time of this criterion. In some protocols, such a criterion is a sign of the end or the specified message size. In other protocols, such a criterion is no data in the input stream for a specified time — the symbol time. In both cases, the criterion waiting time, or the symbol, is a crucial and strongly affects the overall exchange time and the data integrity. Consequently, the smaller this time, the better if you have no loss the data tail. Here the problem of hardware and its drivers latency happens.