In this chapter, we will look at the available modules for the Logix platform, as well as how to configure and use them in a Logix project. We will also include methods for identifying module features by their Logix module and catalog numbers, and introduce the address tree that a typical I/O module creates. After completing this chapter, you will be able to select and add I/O modules to your projects, modify the module configurations, and reference their real-time values using the recommended best practices.

This chapter will cover the following aspects of Logix modules:

Understanding the module terminology
Learning about the module types
Configuring a ControlLogix module
Reading the Logix module catalog numbers
Learning about the module special features
Addressing I/O data
Configuring remote racks with RSNetWorx

This chapter begins by explaining some of the basic Rockwell module terminology.

Technical requirements

To complete this chapter, you will need to create a Rockwell Automation support account by going to https://www.rockwellautomation.com/account/create-account.

Creating an account is free and the material we will review in this chapter is publicly available to anyone who has registered with Rockwell Automation.

You will also need a copy of RSLogix or Studio 5000 that has a license for Emulate 5000to program your project. You can either purchase this from your local distributor or request a time-limited trial version. You can find a local distributor for Rockwell Automation products at https://locator.rockwellautomation.com/.

Understanding the module terminology

Modules provide the interface between a computer and the physical world. There are a wide variety of modules available that perform specific functions in an industrial process. Before we can learn how to use modules in our programs, we need to understand their different properties, functions, and capabilities.

Let's begin by taking a look at some of the common Logix module properties:

Voltage: This attribute is the difference in electrical potential between two points, measured in Voltage A/C (VAC) or Voltage D/C (VDC). When visualizing voltage, I prefer the age-old super soaker (water gun) analogy, where voltage is the pressure (the number of times you have pumped the super soaker).
Current: This attribute is the flow of electrical charge measured in Amps (A) and Milliamps (mA). In the super soaker analogy, this is the diameter of the water gun's nozzle.
Signal: This attribute is the modulation in voltage or current, which relays the operational state of a device. A signal is representative of values such as pressure, temperature, and flow.
Input: This module is wired to detect the values that are sent from the field to the controller. Input values are used to determine, for example, whether a motor is running and the speed of a motor's rotation.
Output: This module is wired to transmit values that are sent from the controller out to the field. Output values are used, for example, to start a motor and tell a motor how fast it should run.
Rack: This attribute is a chassis that contains the controller modules, and typically ranges in size from 4 to 17 module slots. ControlLogix also supports multiple racks that can be connected to each other using communications technology such as EtherNet/IP or ControlNet. Most CompactLogix controllers are mounted along a DIN rail and do not use a rack.
Slot: This attribute refers to a module's position in a rack. The number of slots will vary by rack size and the Logix controller you are using.

Module: This attribute is a modular card that mounts in a slot of a rack or along a DIN rail. This module is used to handle a wide variety of automation tasks and is available from a number of vendors. In this chapter, we will focus on the most common modules, which simply process the input or output signals.
Channel: This attribute is the individual input or output circuit on a module that links one signal connection with a device in the field.
Address: This attribute is the complete path from a Logix controller to a module channel, property, or configuration value.
Adapter: This attribute is the communication module that mounts in a slot on a rack, which enables a controller to communicate with a remote rack over EtherNet/IP or ControlNet. The adapter name is the root of the path to any address for modules located in remote racks.

Now that we have covered the basic components and terminology of Rockwell modules, we will explore the broader module types available in the following section.

Learning about the module types

In general, modules are classified as analog, digital, communication, controller, and specialty. They differ by the number of channels, the ranges of input and output they are capable of handling, and by the special features that are optionally available. In this section, we will explore the base module types and explain the possible feature sets.

In the following sections, we will enumerate some of the most common module types in the ControlLogix and CompactLogix families of controllers. We will cover the basic categories of modules that are available for Rockwell controllers, which include analog modules, digital modules, communication modules, CPU modules, and motion control modules.

Analog modules

Analog modules process the input and output of signals that vary by current and voltage and translate to real-world values, such as pressure, temperature, and flow. Analog modules vary by the number of channels (4 to 16), the operating temperature range, the maximum isolation voltage they can handle, the range of the current (0 mA to 21 mA), and the range of voltage (+/- 25 VDC). There are even combination analog modules that house both input and output channels.

Each analog channel usually requires three wires in order to complete an analog circuit correctly. The way that the channel is wired changes depending on whether you are using voltage or current. Be sure to review the wiring diagrams for your module at the Rockwell Automation Literature Library document referenced in the Further reading section of this chapter.

One of the most common modules used within most control systems is a digital module. In the following section, we will introduce digital modules.

Digital modules

Digital modules process the input and output of signals that vary by current and voltage and translate to either ON or OFF values. Digital modules vary by the number of channels (8 to 32), the operating temperature range, the maximum isolation voltage they can handle, and a range of supported voltage (0 VDC to 146 VDC and 10 to 265 VAC). We will work directly with DC digital input and DC digital output ControlLogix modules in Chapter 15, Building a Robot Bartender in Logix. In the sample application, we will evaluate a number of different digital I/O cards that will work for our Robot Bartender application.

Now that we have covered both digital and analog module types, we will explore some of the other modules, starting with communication modules.

Communication modules

There is a wide range of communication modules available that allows remote rack communications, device communications, and motion control. There are communication modules by Rockwell and third-party vendors that allow the Logix controllers to communicate using the network technologies we talked about in Chapter 6, Industrial Network Communications, and many other non-Rockwell Automation protocols.

Communication modules must be associated with a processor module to interpret and process communication protocols. In the next section, we will briefly discuss the controller processor (or CPU) modules.

Controller processor modules

We covered controller modules in Chapter 2, Understanding ControlLogix, and Chapter 3, Understanding CompactLogix. It is important to remember that ControlLogix can support multiple controller modules in a single rack. Controller processor modules are the CPUs, or brains, of our Logix application and execute our programs to control our processes.

In the following section, we will introduce motion control modules, which are used to manage multi-axis motion devices.

Motion control modules

Motion control is a discipline of industrial automation that involves moving parts of machines in a controlled manner. Motion control is widely used in distribution centers, printing, electronics production, packaging, and assembly (such as an automotive assembly). Motion control is supported within the Logix architecture by a variety of methods. The following is a brief list of methods for interfacing with motion control devices:

Integrated motion on the EtherNet/IP network (for Ethernet-based drives)
Kinetix-integrated motion solutions (uses a Serial Real-time Communications System (SERCOS) or EtherNet/IP interface)
Logix-integrated motion control (the analog family of servo modules for controlling drives/actuators)
DeviceNet networked motion control

In the case of SERCOS, a dedicated SERCOS fiber-optic motion control module can be used for high-speed motion control applications. For more information on motion control modules, please take a look at the 1756 ControlLogix Integrated Motion module specificationslink in the Further reading section of this chapter.

In the next section, we will finish off our coverage of Rockwell modules by providing an overview of some of the specialty modules that are available.

Specialty modules

Specialty modules allow your automation project to perform the following specialized tasks:

High-speed counting:Used to count changes of state within a process control network
Flowmeter measurement:Used to interface with specialty flowmeter equipment and can provide flow and calibration information as Logix tags within a program
Limit switch monitoring: Dedicated modules for monitoring limit switch activation
Hydraulics control: Specialized modules for the control and monitoring of hydraulic systems

Now that we have covered all the various types of modules available within the ControlLogix and CompactLogix families of controllers, in the following section, we will explore some of the wiring solutions available for these modules.

Introducing Logix terminal blocks

In the Logix family, most modules do not come with built-in screw terminals, so Removable Terminal Blocks (RTBs) or Bulletin 1492 Interface Modules (IFMs) must be purchased separately. You should carefully review the wiring requirements for your module using the online Rockwell Automation Literature Library resource (relevant links can be found in the Further reading section of this chapter). We cover RTBs in more detail in Chapter 15, Building a Robot Bartender in Logix, of this book.

Now that we have covered the basic Rockwell module types, we will go through an exercise where we will configure one using RSLogix or Studio 5000.

Configuring a ControlLogix module

In this exercise, we will learn how to add a ControlLogix module to a Logix project and look at a typical module configuration by performing these steps:

First, we will need to open RSLogix 5000/Studio 5000 Logix Designer. Create a new project and select a ControlLogix controller (in my case, I selected 1756-L73 on Slot #0). This process varies between versions of Logix, so we will not show these steps in detail.

Next, we will add the module by right-clicking on the Controller Organizer pane's IO Configuration tree and selecting New Module..., as seen in the following screenshot:

Now, we can select the module we wish to configure. For our example, it will be a digital input module, 1756-IB16D 16 Point 10V-30V DC Diagnostic Input. The Select Module Type window varies from version to version of Logix, but regardless of the software, it is relatively easy to locate our module:

As you can see from the Select Module Type window, there is a wide range of modules that can be added to our rack. As a reminder, it is important to ensure the modules that are added are compatible with your processor and RSLogix or Studio 5000 version. You can always use the Downloads and Compatibility tool that we introduced in Chapter 2, Understanding ControlLogix, to verify compatibility.

Next, we will configure the module by providing these inputs (as shown in the following screenshot):
- Name: R01_S01
- Slot: 1
- Description: DI Module

The following screenshot shows the completed New Module form window:

Next, we can configure the module properties and adjust the setup of the module. Each module in Logix has unique properties and configuration requirements, so it is imperative that you refer to the Rockwell Automation Literature Library document for any module you are configuring. Once you have reviewed the module properties, click on the OK button, as in this screenshot:

c has been configured and you can see it in the Controller Organizer pane in our rack:

As we can see from our I/O Configuration setup, we have successfully added an I/O module to our project. In the next section, we will investigate the meaning of the various numbers and letters used in Rockwell product identifiers.

Reading Logix module catalog numbers

It is helpful to understand the features of a module at a glance simply by reading the device's catalog number. Rockwell has created a standard naming convention for their equipment, which we will explore in this section.

The modules in Integrated Architecture are referred to by their Rockwell Automation catalog numbers. Catalog numbers are made up of four parts, as illustrated in the following diagram:

The preceding diagram breaks apart the catalog numbers for a ControlLogix digital input module with 16 channels and built-in diagnostics.

The Bulletin number is a four-digit identifier for the Logix controller family. ControlLogix begins with the 1756 Bulletin number, the SoftLogix modules begin with the 1789 Bulletin number, and CompactLogix begins with the 1769 or 1768 Bulletin numbers.

The module type is the second part of the Rockwell Automation module catalog numbers. Types that begin with I are input cards and types that begin with O are output cards. Let's take a look at a few sample types for commonly used modules. Digital input types are usually IQ or IG for VDC and IA or IM for VAC. Analog inputs types are typically IF, IR, or IT; digital output types are typically OB for VDC or OA for VAC; and analog output types are typically OF.

Channels are the third part of catalog numbers. Channels represent the number of field signals that can be wired to and processed by the module.

The last part of catalog numbers indicates the special features of the module. The special features indicate any unique capabilities of the module. There are links to the I/O analog and I/O digital module reference materials in theFurther readingsection of this chapter. For more information about the module catalog numbers, please refer to the Rockwell documentation.

We have now learned how to decipher the Logix module catalog numbers. In the next section, we will briefly overview some of the special features you may find on different Logix modules.

Learning about the module special features

In this section, we will detail many of the ControlLogix module features that are available within the Rockwell product lines. It is important to be familiar with these terms as you will frequently encounter them when selecting ControlLogix modules or when reviewing Rockwell documentation on modules.

Special features provide additional support to the Logix modules and some of the following optional features:

HART: This feature allows modules to read the transmitter status and health information or adjust the configuration and calibration of equipment through a Logix controller.
Diagnostic information: This feature provides diagnostic information for each channel on the module. The following diagnostic information values are available in Logix:
- Field Power Loss Detection: When the field power to the module is lost, it can cause values to be misrepresented. Field power loss detection will generate a point-level fault to the controller.
- Open Wire Detection: This feature is used to verify that the field wiring is connected correctly by measuring the minimum leakage current. A leakage resistor must be connected across the contacts of the device in order to provide the minimum leakage current.
- No Load Detection: This feature is a diagnostic feature of a module that detects a break in the field wiring by comparing it to a specified minimum load current (3 mA or 10 mA, depending on the module).
Output state verification: This module confirms with the controller that it received a command and whether the field-side device connected to the module has executed the command.
Electronic fusing: This feature is the internal electronic fusing that prevents over-current through the module.
Individually isolated channels: This feature is the per-point isolation where each channel can be wired with its own individual power source.

Per-point timestamping: This module can be configured to record or latch the time at which a state is changed from ON to OFF, OFF to ON, or both.
FIFO mode operation: This feature stores 160 timestamps, event sequence numbers, status, and input point numbers on the module for recording high-speed events (for example, shutdowns).
Ultra-fast on/off times: This feature is capable of switching within 15 uS.

Some examples of the Logix module catalog numbers are as follows:

1756-IA32: ControlLogix Digital 74-132 VAC Input 32 Pts (36 pin)
1756-IA8D: ControlLogix Digital 79-132 VAC Diagnostic Input 8 Pts (20 pin)
1756-IF16H: ControlLogix Analog Input-16 Point HART

1769-IF8: CompactLogix 8 channel analog current/voltage input module
1769-IQ16F: CompactLogix 16 point high-speed 24 VDC input module

Although this is not an exhaustive list of all the special features found within Logix modules, it does cover many of the commonly used ones. In the next section, we will learn how to address the individual data points found on Logix modules within our RSLogix or Studio 5000 programs.

Addressing module I/O

As we learned earlier in this chapter, channels represent the field signals that can be wired to, and processed by, the module. But how do we reference these channels in our programs and read their values or write new values to field devices? In this section, we will learn the standard syntax for addressing I/O channels. Individual channels on a module can be referenced in your Logix Designer/RSLogix 5000 programs using its address. An address gives the controller directions to where it can find a particular piece of information about a channel on a module. The following diagram breaks down the syntax of a module value reference:

The first field of an address specifies the location of the channel (and is followed by a colon). The location can either be local to the controller or on a remote rack, which connects through a network adapter or bridge module. So, this field can be one of the following bridges:

LOCAL: This module is on the same rack or DIN rail as the controller.
Adapter name: This module is the name you have configured for the network adapter or bridge module, which connects to the remote rack where the module is located.

The second field of an address is the slot number of the I/O module in its rack or DIN rail (and is followed by a colon). The address-slot numbering starts at 0. In the case of CompactLogix (where power supplies can be placed in the middle of the DIN rail), power supplies do not count as a slot position.

The third field of an address is a single letter that represents the type of data. These are the following four types that are specified in an address:

I: Input
O: Output
C: Configuration
S: Status

The fourth field of an address specifies the member data of the I/O module. Different modules store data of different types. For a digital module, a data member usually stores the input or output bit values. For an analog module, a channel member (CH#) usually stores the data for a channel.

The fifth field can be either a property or a bit of a member. A property provides specific data related to a member. A bit provides a specific point on a digital I/O module. The bit range will depend on the size of the I/O module and, like the slot position, it also starts at 0 (0 to 31 for a 32-point module).

Some examples of the Logix module addresses are as follows:

Logix module addresses	Description
`MyRack_3:11:O.Ch4Data`	Channel 4 of the analog output module on slot 11 of the`MyRack` adapter
`Local:3:I.Data.24`	Channel 24 of the digital input module on slot 3 in the local rack
`Local:3:I.Fault.24`	Fault status for channel 24 of the digital input module on slot 3 in the local rack
`Local:3:C.DiagCOSDisable`	Configuration Boolean value for disabling the Change of State (COS) diagnostic information for the digital input module on slot 3 in the local rack

In the following exercise, we will add a reference to a specific value of our I/O module within RSLogix or Studio 5000. Interfacing with I/O modules will allow us to activate pumps, read temperature values, and collect input from operator push buttons.

Exploring module addresses

Modules are the control system's interface to the physical world and they play a critical role in any industrial control system. In this section, we will learn how to read and write data to these critical industrial components.

In this exercise, we will explore the I/O module addresses for the digital module we added earlier in the chapter. Perform the following steps:

First, in the Controller Organizer pane, select and double-click on the Controller Tags option to open the Controller Tags panel, as in the following screenshot:

You will notice that because we added a diagnostic module, there are two address trees associated with the local slot. There is one address tree for the diagnostic configuration type data and another address for the input type data, Local:1:C and Local:1:I:

After expanding the type address space, we can see the member data contained within the configuration and input types.

Under the configuration member addresses, we can view and adjust the configuration values for all the diagnostic features of our I/O module (recall D at the end of the Logix module catalog numbers of the I/O module we selected—1756-IB16D). We can see the configuration member data for COS, open wire, fault latching, and filtering. You can easily modify the configuration of these features by double-clicking on the Value field and entering a new value.
Under the input member address tree, we see the real-time values from our input module. In addition to the normal digital input values, our input module is armed with diagnostic information such as channel faults, channel open wire detection, and channel change of state timestamping. These addresses can be referenced in our program code (ladder logic, function block, structured text, sequential flow diagrams) and evaluated directly in our logic.

The recommended best practice is to buffer the module I/O data before evaluating it in logic. In the next section, we will introduce the concept of module I/O data buffering.

Buffering module I/O data

In Chapter 1,The History of Rockwell Automation Technologies, we briefly looked at the Logix operating cycle and the differences between asynchronous and synchronous execution. In the olden days of PLC-5s and SLC-500s, before we had access to high-performance asynchronous controllers such as the ControlLogix, SoftLogix, and CompactLogix families, program execution was synchronous and very predictable. In an asynchronous controller, there are many activities that appear to be happening at the same time. The input and output values can change in the middle of a program scan and put the program in an unpredictable state. Today, there is a rule, in most automation companies, that requires programmers to write code that buffers the I/O data to base tags that will not change during program execution. We will look at the buffering examples later in the book and also explore a new alternative to buffering I/O available in Logix Designer version 24 and higher using the program parameters.

In modern ControlLogix programs, it is best practice to alwaysbuffer your I/O module data. In the next section, we will learn how we can add remote racks using the RSNetWorx tool.

Configuring remote racks with RSNetWorx

RSNetWorx is a standalone application that is used to configure the Logix network topologies and export them to an Electronic Data Sheet (EDS) file, which we can import into our Logix application. Without an EDS file, we are unable to set up remote racks in an application.

EDS files are a plain text format based on the CAN open standard and used to specify various descriptive and communication data for hardware devices. EDS files are used by RSNetWorx and RSLinx to provide device information, configuration information, and an icon for that device. Device EDS files can be downloaded from the Compatibility & Downloads section of the Rockwell website, referenced in Chapter 2, Understanding ControlLogix

RSNetWorx is on the annual release of the Rockwell Automation toolkit. It can also be found on the Rockwell website as a free download for approved customers and system integrators. There are three versions of the product—one for each Logix network type (EtherNet/IP, ControlNet, and DeviceNet).

The following is a screenshot of the RSNetWorx for the EtherNet/IP software solution from Rockwell:

RSNetWorkx allows users to configure Rockwell device networks using multiple network technologies and network media. It is important to be aware that this tool is used to configure the communication modules that are added to your rack. Remote racks are an advanced topic in the Logix platform and we will not cover this in detail in this book. For more details on RSNetWorx, see Getting results with RSNetWorx for DeviceNet in the Further reading section of this chapter, which is a link to the Rockwell Automation Literature Library document.

Summary

In this chapter, we learned about the types of modules that are available in the Logix controller family. We introduced the basic module terminology that is commonly used in the industry and the procedure for adding modules to our project, as well as demonstrated the methods for addressing the module values. We enumerated the available modules for the Logix platform, learned how to configure them, and explored their use in a Logix project. We also introduced methods for identifying module features by their Logix module catalog numbers and introduced the address tree that a typical I/O module creates. You now know how to select and add I/O modules to your projects, modify the module configurations, and reference their real-time values using the recommended best practices.

In the next chapter, we will begin to work with RSLogix or Studio 5000 to write ladder logic.

Questions

The following questions can be used to test your retention of the concepts introduced in this chapter. You can find the answers to these questions in the back of the book under Assessments:

What is the term for a chassis that contains the controller modules and typically has a range of 4 to 17 module slots?
What attribute refers to a module's position in a rack?
What attribute is the individual input or output circuit on a module that links with one signal connection with the field?
What is the name of the attribute that is the complete path from a Logix controller to a module channel, property, or configuration value?
What module type processes the input and output of signals that vary by current and voltage and translate to real-world values such as pressure, temperature, and flow?
What module type processes the input and output of signals that vary by current and voltage and translate to either ON or OFF values?

Table of Contents for Configuring Logix Modules

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