Rockwell Automation 1756-XXXX ControlLogix Digital I/O Modules - Manual (Page 48)

48 Rockwell Automation Publication 1756-UM058G-EN-P - November 2012
Chapter 3 Common Module Features
Use CIP Sync Time with Fast I/O Modules
The 1756-IB16IF, 1756-OB16IEF, and 1756-OB16IEFS modules use CIP Sync
for both timestamps and scheduling.
CIP Sync is a CIP implementation of the IEEE 1588 PTP (Precision Time
Protocol). CIP Sync provides accurate real-time (Real-World Time) or Universal
Coordinated Time (UTC) synchronization of controllers and devices connected
over CIP networks. This technology supports highly distributed applications
that require timestamping, sequence of events recording, distributed motion
control, and increased control coordination.
The 1756-IB16IF, 1756-OB16IEF, and 1756-OB16IEFS modules are CIP Sync
slave-only devices. There must be another module on the network that will
function as a master clock. For more information on how to use CIP Sync
technology, see the Integrated Architecture and CIP Sync Configuration
Application Technique, publication
IA-AT003 .
Fast I/O modules can be used to capture timestamps and schedule outputs like
CST-based modules while providing the following advantages:
• Fast I/O modules have much higher precision than CST-based modules.
• Inputs are timestamped by point, so multiple inputs can be configured for
COS without losing timestamp data.
• CIP Sync is system wide, so timestamp and schedule values are consistent
across all modules in the system. For instance, using 1756-IB16IF input
timestamps to schedule outputs on a 1756-OB16IEF module means the
controller, input module, and output module are not restricted to the same
chassis as is the case with CST-based I/O.
• Output modules use all 64 bits of the timestamp to schedule, so there are
no limits on schedule ranges.