Watlow PM LEGACY™ Limit Controller • 97 • Chapter 8 Features
CIP Implicit Assemblies
Communications using CIP (EtherNet/IP and DeviceNet) can be accomplished with any PM Integrated
control equipped with either DeviceNet or EtherNet/IP communications cards. As was already men-
tioned, reading or writing when using CIP can be accomplished via explicit and or implicit communi-
cations. Explicit communications are usually executed via a message instruction within the PLC but
there are other ways to do this as well outside of the focus of this document.
Implicit communications is also commonly referred to as polled communications. When using implic-
it communications there is an I/O assembly that would be read or written to. The default assemblies
and the assembly size is embedded into the firmware of the PM control. Watlow refers to these as-
semblies as the T to O (Target to Originator) and the O to T (Originator to Target) assemblies where
the Target is always the PM LEGACY™ Limit Controller and the Originator is the PLC or master on the
network. The size of the O to T assembly is initially set to 40 (32-bit) members where the T to O as-
sembly consists of 40 (32-bit) members. All assembly members are user configurable with the excep-
tion of the first T to O member. The first member of the T to O assembly is called the Device Status,
it is unique and cannot be changed. If the module has been properly configured when viewing this
32-bit member in binary format bits 12 and 16 should always be set to 1 where all of the other bits
should be 0. All other members that follow Device Status are user configurable. The Appendix of this
User’s Guide contains the PM implicit assemblies (See Appendix: (CIP Implicit Assembly Structures).
Modifying Implicit Assembly Members
To change any given member of either assembly (T to O or O to T) simply write the new class, in-
stance and attribute (CIA) to the member location of choice. The CIP communications instance will
always be instance 2.
Profibus DP - (Decentralized Peripherals)
This protocol is typically used to operate sensors and actuators via a centralized controller within
industrialized production topologies. Data rates up to 12 Mbit/s on twisted pair cables and/or fiber
optics are possible. This protocol is available in three functionally graded version; DP-V0, DP-V1 and
DP-V2. It should be noted that Watlow products utilizing this protocol support DP-V0 and DP-V1 only.
DP-V0 - provides the basic functionality of DP, including cyclic data exchange, station, module and
channel specific diagnostics and four different interrupt types for diagnostics and process
interrupts.
Cyclic Data refers to input/output data that is pre-configured to pass from the Profibus-DP Class 1
Master and the Slave at a known rate. Cyclic data is expected on both the sender and the receiver
end of the message.
Note:
To use DP-V0 (cyclic data transfer) first configure and then register the General Station Description
(GSD) file. Watlow provides a software tool allowing for total customization of the data to be read
and or written to. Acquire this software tool (Profibus GSD Editor) via the CD that shipped with the
product or, as an alternative, point your browser to: http://www.watlow.com/en/resources-and-sup-
port/Technical-Library/Software-and-Demos and navigate to the bottom of the page and click on
“Software and Demos” to download the software.
Using the GSD Editor a user can configure up to a maximum of 244 I/O bytes that can be read or
written to from Zone 1 through 16. DP-V1 - contains enhancements geared towards process automa-
tion, in particular acyclic data communication for parameter assignment, operation, visualization and
interrupt control of intelligent field devices, in conjunction with cyclic user data communica-
tion.
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