Rockwell Automation 1738 Assembly Connections for POINT I/O and ArmorPOINT I/O EtherNet/IP Adapters - Manual (Page 13)

Publication 1734-UM016A-EN-P - October 2010
Configuration 7
When Fixed Boundaries are selected, the formula for mapping is:
H+(N-1)(size per slot), where N = slot position and H is the size of the
optional status header (8 if used, 0 if not used).
The choice of alignment is highly dependent on the originator used and
application-specific requirements.
• If data size is at a premium, Byte alignment is the most efficient choice.
• If the originator can only process data on DINT boundaries (as is the
case with RSLogix controllers), then Double Word alignment should be
used.
• If ease of programming is desired, the Fixed Boundaries option allows
for easy location of the data within the data packet. Additionally the use
of Fixed Boundaries along with the 1734-ARM module will allow
modules to be added later without having the location of any slot's data
change. The ARM module will reserve data space for future modules.
Since each slot occupies the same size in the data image, when the ARM
module is replaced with a future module, the data boundaries are
preserved.
Individual Module Configuration Options
The request for an Assembly connection is accepted with or without a
configuration assembly present. If a configuration assembly is present, it must
contain the minimum information presented in the Configuring the
Connection section. See Table Minimal Adapter Configuration Assembly on
page 5. If individual module configuration is required, it can be appended to
the end of the minimum configuration structure for any or all modules that
require configuration. The construction of this configuration data structure is
a manual process.
Alternatively any tool that is capable of sending CIP packets can configure the
parameters of individual POINT I/O modules. The configuration is stored
locally in the module's non-volatile storage. When the configuration is sent
from the connection originator via the connection request, the adapter also
stores a copy of this configuration and restores it if that module is ever
replaced. This is similar to the Automatic Device Replacement feature of
DeviceNet scanners. If the configuration is sent from the connection
originator via the connection request, the configuration assembly size is
limited to the maximum packet size of 510 bytes. This may be an issue in larger
systems that require module configuration. Configuring modules through a
separate tool will allow the configuration to be sent to modules individually,
effectively eliminating the packet size limitation. Furthermore, the
configuration tool of choice may provide a rich graphical user interface,
reducing the possibility that configuration is incorrectly entered. One such tool
is RSNetWorx for DeviceNet.