Special characteristics of DNP3 communication
Data transmission only following changes
- Change-driven transmission of process data between RTU and control center
- Signaling of failures in connection, RTU or control center
- Automatic data updating for all communication partners involved following troubleshooting and following the startup of the RTU or control center
Chronological processing of process data
- Time tagging of all data frames at the place of origin allows process data to be archived by the process control system in the correct chronological order
- The time of the DNP3 stations in the WAN can be synchronized via SIMATIC PCS 7 (including summertime/wintertime switchover)
Data storage on site
- During the failure of the connection or the communication partner, the TIM communication module can temporarily store (for several hours or even days) up to 200 000 events
- Intermediate storage of message frames of lower priority in the case of priority-controlled data transmission, e.g with quantity-dependent data transmission costs
Modes
The communication mode between the control center and RTU depends on the telecontrol protocol, the type of WAN, and the telecontrol configuration.
The DNP3 telecontrol protocol supports the following operating modes (functional principle similar to that described in the section "Telecontrol with SINAUT ST7"):
- Polling
- Polling with time slot procedure
- Spontaneous mode in the TCP/IP-based WAN