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6-16
Peer-to-Peer Messaging
Stagger the Messages
Route PLC-5 Messages
Between ControlNet
Networks
Publication CNET-UM001C-EN-P - November 2005
As you add messages to your project, you may have to coordinate the
execution of the messages. To avoid errors and assure that each message is
processed, follow these rules:
Rule 1
Enable no more than 16 messages at one time (including block transfers).
Rule 2
Enable no more than 10 of the following types of messages at one time:
• CIP data table reads or writes that are not cached
• CIP generic
• PLC-2, PLC-3, PLC-5, or SLC (all types)
• block transfer reads or writes that are not cached
If the number of messages in your application exceeds rules 1 and 2, then
stagger the execution of your messages. Here are some options:
• Send each message in sequence.
• Send the messages in groups that are within the limits of rules 1 and 2.
• Program a message to communicate with multiple devices.
You can use ControlLogix communication modules to route a message
between PLC-5 controllers that are on different networks, such as a bridged
message. The following example depicts a ControlLogix chassis with two
1756-CN2 modules that route a message from one ControlNet network to a
different ControlNet network.
Message from a PLC-5C on a ControlNet network to a
EXAMPLE
PLC-5C on a different ControlNet network
P
L
C
5
C
C
N
2
ControlNet
Node 3
Network A
Node 2
Message
C
N
2
Node 5
ControlNet
Network B
Node 1
P
L
C
5
C
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