The Manager RPM of 2541 Redundant Processor permits the control engineer to make a warm system backup for Simatic® 505 or CTI 2500 Series PLCs. Both the main PLC and standby PLC work in run asynchronously mode. To avoid deviation of the controllers, important variables may be moved to the standby PLC every scan. The main and standby PLCs are physically linked to the remote bases through the RPM. Both PLCs communicate to the RPM via the channel of remote I/O communications. The RPM observes the communication transactions on the link of remote I/O and mirrors the information to the standby PLC when it asks for the status of remote I/O points. The product of RPM shows to the system control as a remote base in the memory map of I/O. Additionally the RPM might be organized as multiple bases of virtual remote. These remote bases include slots of virtual I/O up to sixteen pairs of 32 WX/WY. These points of virtual I/O might be used to move important variables to the standby PLC every scan. The main PLC transfers defined important data to unused address space of WY and the standby PLC transfers data from unused address space of WX to the related data element. Once the important data is mapped to the link of remote I/O, the PLC assurances the data to be moved every PLC scan.
This RPM Home base contains of 32Y and 32X I/O points with an optional 14 sets pairs of 32WX/32WY. The separate inputs offer status information to the main and standby PLCs. The points of input are utilized to steer ladder logic and to check if checksums have changed in the PLCs. The separate outputs are utilized as control bits in the program of ladder logic to start transfers, and to create pulses of “heartbeat”. These pulses are checked by the RPM to notice scan malfunctions or a changeover to programming mode. The pairs of WX/WY are used to move the important variables.