Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 256)

Publication AG-UM008C-EN-P - February 2005
7-30 Configuring Logix Controllers
Considerations When Configuring MSG Control Blocks
Keep these considerations in mind when configuring serial port
messages between a Logix controller and other controllers.
•
The connection path for serial port messages always begins with
either a ‘2’ or a ‘3’ to indicate send out the first or second serial
port (as opposed to a ‘1’, which would indicate send to the
backplane).
•
Leave the Communication Method as CIP.
•
Leave the message configuration Cache Connections unchecked,
as message connections passing through the serial port cannot
be cached, regardless of this setting.
•
CIP Data Table Read and Write message types are sent as
connected messages, which means every time a MSG of one of
these types is triggered, there are three command packets that
are transmitted: a make connection command, the read or write
command, and a break connection command. This is very
inefficient use of serial communication bandwidth.
•
PLC5 and SLC Typed Read and Write message types are sent as
unconnected messages, which means only one command packet
is transmitted every time a MSG of one of these types is
triggered. Therefore, even when initiating to another Logix
controller, it is much more efficient to use a PLC5 Typed Read or
Write message type.
•
Logix uses either logical ASCII addressing or symbolic
addressing for PLC5 Typed Read or Write message types. To
address a Logix tag directly, use symbolic addressing by entering
in @tagname for the Source or Destination Element field, where
tagname is a defined controller scoped tag in the receiving
Logix controller. To address a PLC-5 controller file, use logical
ASCII addressing by entering in XY:Z for the Source or
Destination Element field, where X is file type status (S), integer
(N), bit (B), or float (F), Y is the file number and Z is the starting
element number. This format may also be used to read or write
a Logix controller tag, if that tag has been mapped in the
receiving Logix to a ‘PLC 3,5/SLC’ file number. For PLC-5 file
type float (F), the Source or Destination Tag in the initiating
Logix must be of type REAL. For the other valid PLC-5 file types,
the Source or Destination Tag in the initiating Logix should be of
type INT.
•
The SLC Typed Read and Write message types can only be used
to read integer (N), binary (B), and long (L) data files in SLC 500
and MicroLogix controllers where available. The Source or
Destination Tag in the initiating Logix should be of type INT.