Rockwell Automation Publication 1756-PM020F-EN-P - January 2019 75
Chapter 4
CIP Over the Controller Serial Port
The information in this chapter provides guidelines for communicating with
ControlLogix controllers that use CIP over the serial port. For more
information about DFI, see the
DF1 Protocol and Command Set Reference
Manual, publication 1770-6.5.16. For more information about CIP services
used with Logix 5000 controllers, see CIP services.
The serial port of the controller supports the DF1 protocol and PCCC
commands. Also deliver CIP messages and CIP services by encapsulating
CIP explicit messages inside of the PCCC commands 0x0A and 0x0B.
PCCC has an inherent format limit of 244 bytes of application data. If an
application sends a message larger than 244 bytes, it returns an error. The
PCCC commands support a PCCC fragmentation protocol to allow the
transmission of larger CIP messages (up to 510 bytes). For more information,
see Fragmentation Protocol.
See also
CIP services on page 13
Unconnected Messaging (UCMM) through PCCC on page 75
Connected Explicit Messages through PCCC on page 76
Fragmentation Protocol on page 78
PCCC Command Code 0B provides CIP unconnected explicit-message
capability over the controller's serial port. Use this for infrequent requests to
the controller (for example, to read or write ControlLogix tags) or to
establish an explicit message connection with the controller. See Connected
Explicit Messages through PCCC for connected communication.
The content of this PCCC message is a CIP explicit-message service request
or response, such as those described earlier in this manual.
Name Type Description of Request Parameter Semantics of Values
CMD USINT Command = 0x0B
STS USINT Status (0 in request) See the DF1 Protocol and Command Set Reference
Manual, publication 1770-6.5.16.
TNSW UINT Used to match response with request
(UCMM) through PCCC
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