CTI 2572-A, Installation And Operation Manual

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CTI 2572-A Installation and Operation Guide V1.3 31
CHAPTER 5. CAMP CLIENT COMMANDS
5.1. Overview
The CAMP client commands are used when you wish to use PLC logic to initiate communications.
This function may be used for peer to peer communications among PLCs or to send unsolicited data
to your HMI application. For example, you might use this function to report alarms to a supervisory
PC, avoiding the requirement to continuously poll for alarm data.
NOTE:
If you are using the 2572-A in Server mode only, you can skip the this chapter
5.2. CAMP Multicast Operation
Firmware versions 2.00 and above provide support for IP Multicast. Using multicast, you can write
data to multiple modules using one command. This reduces network loading and simplifies the client
logic.
The TCP/IP protocol reserves a block of IP addresses (224.0.0.0 through 239.255.255.255) for
multicast use. 2572-A modules can be configured to accept packets with one of these addresses.
When a packet with the specified address is received, the message is passed to the CAMP server,
which processes the command. Unlike the typical unicast address, multiple modules can have the
same multicast address; thus, a single packet can be used to update multiple modules. Modules that
are not configured with a multicast address or that use a different multicast address do not process the
message. This allows you to create a group of modules that will participate in a specific multicast
session.
You can configure a 2572-A to receive on a multicast address using the same methods used to
establish the other TCP/IP network parameters.
1. If you are using the PLC Start method, the multicast address can be specified in the Start
Network server command block. See
Section 4.2. Start Network Server Command Block.
2. If you are starting the module using IP parameters stored in EEPROM, you can use the Web
Server interface to enter the multicast address.
3. If you are using DHCP, you can add the multicast address to the parameters that are provided
by the DHCP server.
Caution:
To prevent inadvertent overwriting of V memory data in other PLCs, ensure that only the
modules that you want to participate in the multicast session are configured with the
multicast address.