User manual

100 Publication LOGIX-AP010B-EN-P - May 2010
Chapter 4 Additional RSLogix 5000 Features
The RSLogix 5000 time-based objects provide the foundation for clock
synchronization for multi-CPU systems, accurate motion control functionality,
scheduled output switching to 100 µs accurate, input-event timestamping,
scheduled analog sampling, safety I/O monitoring and communication,
motion cam position calculations, and Wall Clock Time.
Timestamped Inputs
Timestamp is a RSLogix 5000 functionality that records a change in input data
with a relative time of when that change occurred (CST time). With digital
input modules, you can configure a timestamp for changes of data and use the
timestamp to compare the relative time between data samples. This feature
allows for accurate calculations between events to help identify the sequence
of events in fault conditions or during normal I/O operations.
Because only one timestamp value is returned to the controller when any input
channel changes state, only use timestamping on one input point per module.
This value will appear in one of the tags automatically generated when the
module is configured as show below.
Timestamping on multiple input points can be achieved with a Logix Sequence
of Events module. This is a DC input module that provides timestamping on a
per-point basis and the normal functionality of a digital input module. There
are two type of Logix Sequence of Events Modules namely:
• 1756-IB16IS0E – 24/48V DC inputs.
• 1756-IH16IS0E – 125V DC inputs.
Scheduled Outputs
With digital output modules, you can configure the module to set the outputs
at a scheduled time with reference to the CST.
Scheduled outputs can be used in conjunction with the timestamped inputs
feature so that after input data changes state and a timestamp is generated, an
output point will actuate at some configured time in the future. You can
schedule outputs up to 16.7 seconds into the future.
This allows the user to achieve unparalleled accuracy in linking outputs to time
references for applications such as axis positions in motion control, or process
control functions, without putting a huge burden on the communication and
logic processing systems and related application code.