Rockwell Automation 56AMXN/B ControlLogix AutoMax Comm Module - Manual (Page 16)

Page 16 AutoMax DCSNet /RE RIO Module
Publication number 56AMXN-UM002A-EN-P November 2002
Connections and Tags
Connections
When you add a 56AMXN to the I/O Configuration of a ControlLogix, a
broadcast data connection and from one to eight data connections are
created. The number of connections is determined by the Comm Format
you select when you add the 56AMXN module.
The broadcast connection always updates every 3 ms.
The data connections update at a rate from 3 ms to 750 ms, based on the
RPI selected on the Connection tab for the module entry. All data
connections update at the same rate.
The broadcast connection contains the broadcast data the DCS master
transmits. If the 56AMXN is the DCS master, the ControlLogix writes
to output data in the broadcast connection to send the data to remote
drops. If the 56AMXN is a DCS slave, the ControlLogix reads input
data from the broadcast connection to receive the broadcast data
transmitted by the master.
The data connections contain the drop data. Each data connection
consists of 7 blocks of data. Each block contains the input data and the
output data for one drop. You select which drops are mapped into a
block by writing to the Config (C) tag for the 56AMXN. Input and
output data for different drops can be mapped into the same block. The
same drop cannot be mapped to more than one block. By default the
blocks are mapped to consecutive drops.
The number of drop data tags created depends on the type of connection
you select when you add the 56AMXN to the I/O configuration, for
example, Master – Drops, Master, 14 Drops, Slave – 7 Drops, etc. You
cannot change the Comm Format after you create the module; to change
the Comm Format you must delete the current module and create a new
one.
Listen Only Comm Formats
You can also create a 56AMXN in the I/O Configuration with a listen
only Comm Format. A listen only Comm Format lets the ControlLogix
receive only input data. An owning connection must exist for a listen
only connection to work. The listen only Comm Format must be the
same size as the owning Comm Format or smaller.
A listen only connection has no configuration data. All configuration is
done in the owning connection.
For example, if one ControlLogix uses a Master – 28 Drops Comm
Format to a 56AMXN, another ControlLogix can use a Master – Listen
Only 28 Drops Comm Format to obtain input data from to the same
56AMXN. (It can also use a 7, 14 or 21 Drops Listen Only Comm
Format as well.) The ControlLogix with the listen only Comm Format