Rockwell Automation 1755-OF8 GuardPLC Controller Systems - Manual (Page 202)

202 Publication 1753-UM001C-EN-P - March 2010
Chapter 18 Introduction to EtherNet/IP Communication
Data Limits
GuardPLC Controller as an Adapter
Up to 64 assemblies of any type (input or output) can be configured
in one GuardPLC controller acting as a target, as long as the maximum
transmit or receive data is not exceeded. However, because there are
always 2 scanner assemblies, the true maximum for adapter
assemblies is 62. These assemblies must have instance numbers in the
range of 120…183. All input adapter assemblies and the input scanner
assembly together should not exceed 16K in size. Likewise, all output
adapter assemblies and the output scanner assembly together should
not exceed 16K in size.
If an adapter assembly is used for Class 1 PCCC access, its size is
limited only by the total buffer size for all of the assemblies listed
above. However, if the adapter assembly is used for Class 1 implicit
access, the size of the assembly should not exceed 502 bytes. This is a
limitation that EtherNet/IP protocol puts on any EtherNet/IP adapter.
These 502 bytes include a Run/Idle status header, if the output
assembly is configured to use the header. When the Run/Idle header
is used, the actual maximum size for the data is 498, because the
header uses 4 bytes. A similar limitation applies for explicit CIP access.
If the adapter assembly is used only for PCCC access, its size can
exceed the 502 byte limit. Any one PCCC command cannot address
more than 244 bytes. However, an offset can be specified to allow
access to any assembly portion up to a maximum of 16K.
GuardPLC Controller as a Scanner
The Scanner (GuardPLC controller) can connect up to 32 connections,
which can be configured in different targets.
IMPORTANT
In addition to the Ethernet/IP protocol, other protocols (for
example, PROFIBUS-DP, TCP S/R, and others) can also be
executed on a GuardPLC controller at the same time.
A total of 16284 bytes of data can be transmitted and received
per GuardPLC controller. These 16284 bytes can be arbitrarily
divided between the protocols. However, the system signals for
the configured assemblies must be subtracted from the
maximum of send and receive data.