Let's say your question involves Ethernet exchanges between a CP443-1 and a CP343-1. Here are a few pointers:
· Configuring and interconnecting the hardware
Create both CPUs in the same project. Use the HWConfig editor of Step 7 to configure each PLC, including teh communication CPs. Attribute to each CP an adequate Ethernet address, subnet mask and default gateway address. Save and download.
Connect the CPs with CAT5 Ethenet cables to a hub (preferably a switch, if there will be any significant amount of data transfered on the network).
· Configuring the communication service
From the HWConfig editor, open Netpro. Make sure bot CPs are connected to the existing Industrial Ethernet line. Clicking on the network line or on any of the CPs will open a configuration table, where you setup a connection between the partners over TCP/IP. Keep the details of the connections handy (ID number, especially). Save and download to both CPUs.
· Creating the user program
From the program folder, open OB1(for example); call AG_SEND (FC5) and FC_RCV (FC6) from the communications library and insert them in your program. Notice that there are 2 distinct libraries, one for S7-300, one for S7-400, make sure you use the correct one fopr each CP. Use the information from Netpro to setup the communication partners in the program.
Open the online helps for more details and programming information on AG_SEND and AG_RCV.
Save and download to each CPU its own program.
· Start-up and diagnostics
Test the link, verify the status of all communication blocks, check if the selected data is correctly transfered to the communication partners.
Be aware of the differences between AG_SEND/RECV and AG_LSEND/LRECV because involves changes in the hardware editor (>240 bytes or not) according the version of the CP-343 (EX10 or newer) also depending on the version of the firmware of the CP (2.3.x or older).
For all CP models of 400 you have AG_SEND/RECV for the small packets (less than 240 bytes) and AG_LSEND/LRECV for the big packets, but for the 300 you may use AG_SEND (v4.2) or AG_SEND (v3.0) or AG_LSEND (v3.0) depending on CP hardware + CP firmware combined with harware configuration.
Also the documentation in english has some errors and typos, the manual in german is correct.
