6 NetLinx Explicit Messaging Data is exchanged using MSG read/write instructions For best operation MSG instructions should be in the Control Room ladder
7 NetLinx Implicit Data Exchange Ethernet Remote IO Each remote chassis requires 70Kbits/sec (radio network offers 100Kbits/sec). The transfer car operates poorly with significant delay. Why? Reason: The ethernet switch and radio filter cannot block implicit remote IO traffic from the Build Area so is getting into the RF and consuming bandwidth. Fix: Use a switch that supports IGMP snooping.
8 DF1 Wireless Wireless modems provide full support for DF1 protocol Simple, no handshake interface for all applications Operate identical to documented configuration and programming examples May be used with –KE, -KF2, -KF3, AIC, netENI, netDNI and other DF1 interfaces for RTU interfacing or network bridging
9 DF1 Point to Point RS232 Channel 0 DF1 Full Duplex Mode
10 DF1 Multipoint DF1 Polling Master Tank 1 Tank 2 Pump Stations Note: A DF1 master provides data forwarding such that slave to slave communications is permitted.
11 DF1 Protocol over DH485 Network
12 Regional Two Tiered Network
13 Channel Pass-Through SLC5/x processors offer channel pass-through. In the prior example all tier two equipment is directly accessible via Ethernet
14 Example: DF1 Radio Modem Protocol
15 Design Tips Minimize data throughput Reduce the number of MSG instructions by organizing data sequentially in the same file so a single MSG can be used rather than several. Link MSG instructions such that when one completes it enables the next with the last MSG enabling the first MSG. MSG when necessary, perhaps on Change Of Value (COV) Given a choice its better to MSG read/write from the PLC connected to the master radio. Do not exceed radio equipment throughput
16 Design Tip – DF1 A Missing Remote causes other DF1 nodes to fail. This is due to ladder logic design. Dont do this: Reason: with SLC or MicroLogix multiple enabled MSGs are queued in the CH0 message buffer. While queued their Timeout interval is timing. If the current MSG times out others queued will also timeout.
17 Design Tip – DF1 Enable one CH0 MSG at a time and when its complete, enable the next. One method:
18 Design Tip – DF1 Polling Master Driver The parameters Max Pkt Wait Time (Sec) and Max Retransmission Wait Time (Sec) and not well documented. Values that work well: Max Pkt Wait Time: 8 (default 150) Max Retransmission Wait Time: 15 (default 600)
19 Design Tips – Logix Platforms Logix Platforms These machines can REALLY move ethernet data and quickly overwhelm a radio network. As always, do not exceed the networks throughput capability. Be mindful of RPI. Ten 32 bit words with an RPI of 10 milliseconds is 32kbps without even considering protocol overhead.
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