Frame Collision Model and Queueing Strategy of Multiple Callings Based on RS232C Protocol

The communication model of One Master to Multiple Slaves in DCS (Distributed Control System), which is out of RS232c protocol, limits the ability for DCS to respond and deal with the random requests from monitoring and control terminals. The circuit principle and the communication topology of RS232C interface are analyzed to reveal the mechanism of multiple callings from terminals. Poisson distribution is introduced to describe the calling process and develop the multiple frame collision model. A collision probability depends on calling frame format, Baud rate and calling frequency. The collision can be listened, identified and compensated with another calling. It is showed that the communication strategy of multiple terminals calling to central computer with RS232C protocol is feasible.