494 Rockwell Automation Publication 1444-UM001D-EN-P - June 2018
Appendix A CIP Objects
Attribute Semantics
The module calculates instance attributes 2...9 to make sure that the channel
pair is active long enough for valid measurements (overall, TWF, and FFT) to
be made. That DAQ (data acquisition) time represents the minimum that is
required. If desired, you can then extend that time by use of the configured
multipliers, attributes 16...19.
Behavior
Multiplexing provides a means of using all 4-channels of a module in a
situation where the required processing can only be implemented on two or
less channels at a time. Examples are gSE or 40 kHz modes where only one
channel pair can be active due to the high sample rate and signal processing
required. By using 'Paired channels' Multiplexing mode the module
automatically switches between channel pairs, which makes measurements as
each pair becomes active (note that module transducer power is not switched).
In paired mode the time slots are allocated as follows:
• Time slot 0 - channels 0/1
• Time slot 1 - channels 2/3
• Time slot 2 - channels 0/1
• Time slot 3 - channels 2/3
Based on the configured Normal CM data requirements (and other
considerations as appropriate), the module advises and implements the
minimum DAQ (Data Acquisition) Time to allow those measurements to be
properly serviced. As Advanced CM data is based on ad hoc, on-demand
requests (potentially for higher number of lines, different averaging) this is not
automatically catered for. If it is planned to send more demanding Advanced
CM Data requests, then this is allowed by suitably increasing the time
multiplier to a value greater than 1 (attributes 16...19).
The module maintains circular sample buffers of much greater depth than
required for the longest TWF or highest line FFT, this depth is used to
advantage in Multiplexing and Cross Module Synchronization modes.
Likewise there are large circular buffers for corresponding Tacho Times. The
(size) relationship between these two buffers is 16:1. For example, a full set of
Tacho Times is available whenever the sample rate (synchronous or
asynchronous) is equivalent to at least 16 samples per revolution.
Table 244 - Common Services
Service Code Implementation Service Name Description of
Service
Class Instance
0x0E x x Get Attribute
Single
Returns the
contents of the
specified
attribute
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