Gateways. There are several of them. They add a new point of failure, but some times it's just the way to go.
Newer AB EWEB cards can do socket comms, but from what I've read, they are a hassle to set up properly. As you have to handle (dis-)connections yourself.
We're using gateways atm and they are working rather well (once you get the OEM booted from the plant so you can correctly configure the messaging on the AB side
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The major problem with creating a proper Ethernet/IP protocol/interpreter in Siemens is because it doesn't handle variable length in Ethernet comms really well. If you don't know the length of the received message before receiving it, you have to handle it byte per byte until you reach the last byte of data. Just using max size WILL screw you over.
And the fun part? It's one byte per PLC scan cycle. You can't create a loop that reads the entire buffer in one PLC scan. So 50 bytes of data = 50 scans. Easily 200ms.
The HMI-route was one of our options, if we couldn't get the gateways set up. For €700 you can get simple ones that can connect to both Siemens and AB, where you just copy the value from one tag to the other. As mentioned earlier, expect realistic min update rates of 500ms.
Newer AB EWEB cards can do socket comms, but from what I've read, they are a hassle to set up properly. As you have to handle (dis-)connections yourself.
We're using gateways atm and they are working rather well (once you get the OEM booted from the plant so you can correctly configure the messaging on the AB side
)The major problem with creating a proper Ethernet/IP protocol/interpreter in Siemens is because it doesn't handle variable length in Ethernet comms really well. If you don't know the length of the received message before receiving it, you have to handle it byte per byte until you reach the last byte of data. Just using max size WILL screw you over.
And the fun part? It's one byte per PLC scan cycle. You can't create a loop that reads the entire buffer in one PLC scan. So 50 bytes of data = 50 scans. Easily 200ms.
The HMI-route was one of our options, if we couldn't get the gateways set up. For €700 you can get simple ones that can connect to both Siemens and AB, where you just copy the value from one tag to the other. As mentioned earlier, expect realistic min update rates of 500ms.
