Thread Starter: Anit Kumar Started: 6/26/2013 8:45 AM Replies: 7
PPI is a master-slave protocol: the master devices send requests to the slave devices, and the slave devices respond. See Figure 7-7. Slave devices do not initiate messages, but wait until a master sends them a request or polls them for a response.
Masters communicate to slaves by means of a shared connection which is managed by the PPI protocol. PPI does not limit the number of masters that can communicate with any one slave; however, you cannot install more than 32 masters on the
S7-200 CPUs can act as master devices while they are in RUN mode, if you enable PPI master mode in the user program. (See the description of SMB30 in Appendix D.) After enabling PPI master mode, you can use the Network Read or the Network Write instruction to read from or write to other S7-200s. While the S7-200 is acting as a PPI master, it still responds as a slave to requests from other masters. PPI Advanced allows network devices to establish a logical connection between the devices. With PPI Advanced, there are a limited number of connections supplied by each device. All S7-200 CPUs support both PPI and PPI Advanced protocols, while PPI Advanced is the only PPI protocol supported by the EM 277 module.
Module Baud Rate Connections
S7-200 CPU Port 0 9.6 kbaud, 19.2 kbaud, or 187.5 kbaud - No of Connections = 4
Port 1 9.6 kbaud, 19.2 kbaud, or 187.5 kbaud No of Connections =4
EM 277 Module 9.6 kbaud to 12 Mbaud No of Connections =6 per moduleI have also attached the page extract from S7-200 panel for ready referenceHope this helpsCheersNavnag