An Introduction to RSLogix5000 Tags

Tags are the method for assigning and referencing memory locations in Allen Bradley Logix5000 controllers. No longer are there any physical addresses such as N7:0 or F8:7 which use symbols to describe them. These have been replaced with tags which are a pure text based addressing scheme. This is a departure from the more conventional ways of programming PLC’s, which includes Allen Bradley’s earlier line of PLC5 and SLC 500 controllers.

One of the hardest transitions from the older systems is realizing how the tag database works. The person with experience in Allen Bradley systems will recognize many of the instructions and be at home with the editor in RSLogix 5000. Understanding the tag database is the first major hurdle in becoming comfortable with the ControlLogix and CompactLogix systems. So let’s dig in and get started.

The Way We Used To Be

Earlier Allen Bradley PLCs programmed with RSLogix 5 and RSLogix 500 software had data files to store I/O and other internal values. These different data files could only hold one data type. A data type defines the format and the size of the stored value.

Default Data Files

Data File Descriptions

While this method made it easy for using instructions, it provided a challenge for logically grouping different data types together according to function. For instance, in machine control, a motor may have a start, stop, speed and alarm code each with its own data type. Thus, the data was “scattered” throughout the data files.

Comparing the Old and New

The Logix5000 controllers have done away with data files and in its place is the tag database. The tag database organizes memory locations in one place. Each tag is assigned its own data type. The table below shows the association between the current data types and the older systems with data files.

Creating a Tag

One way to create a new tag is right click on the Controller Tags in the Controller Organizer and select New Tag. Even faster is the Ctrl+W hot key.

The following dialog box pops up.

The Name given to the tag has the following rules:

• only alphabetic characters (A-Z or a-z), numeric characters (0-9), and underscores (_)
• must start with an alphabetic character or an underscore
• no more than 40 characters
• no consecutive or trailing underscore characters (_)
• not case sensitive

While tags are not case sensitive, it is good practice to mix cases for readability. It is much easier to read Line1_Start then LINE1START or line1start.

In addition, the tag database list sorts alphabetically. Therefore, it is best to use similar starting characters when you want tags to be together in the monitor list.

Use the Description field for a longer description of the tag. It is best to keep names short yet not cryptic. Tag names are downloaded and stored in the controller but the description is not as it is part of the documentation of the project.

The tag Type defines how the tag operates in the project

Alias tags mirror the base tag to which they refer. When the base tag value changes so does the alias tag. Use aliases in the following situations:

• program logic in advance of wiring diagrams
• assign a descriptive name to an I/O device
• provide a more simple name for a complex tag
• use a descriptive name for an element of an array

Produced and consumed tags make it possible to share tags between controllers in the same rack or over a network. This article does not cover this aspect.

Select a Data Type for the tag by typing it in or by clicking on the ellipsis button and selecting it from the list. A data type is a definition of the size and layout of memory allocated for the created tag. Data types define how many bits, bytes, or words of data a tag will use.

The term Atomic Data Type refers to the most basic data types. They form the building blocks for all other data types.

Logix5000 controllers are true 32-bit controllers, meaning the memory words are 32-bits wide. No matter what, a tag always reserves 32 bits of memory even if it is a Boolean or integer data type. For this reason, it is best to use a DINT when dealing with integers. Furthermore, a Logix5000 controller typically compares or manipulates values as 32-bit values (DINTs or REALs).

A Logix5000 controller lets you divide your application into multiple programs, each with its own data. The Scope of the tag defines if a tag is global (controller tags) and therefore available to all programs or local (program tags) to a select program group. Pay careful attention to this field as creating it in the wrong area may lead to some confusion later on as to its location.

Controller Tags are available to all programs. You cannot go wrong using controller scoped tags unless you easily want to copy and paste programs. A tag must be controller scoped when used in a Message (MSG) instruction, to produce or consume data and to communicate with a PanelView terminal.

Program Tags are isolated from other programs. Routines cannot access data that is at the program scope of another program. Having program tags make it easy to copy/paste programs and not have to worry about conflicting tag names. Make sure though that no controller tags are named the same as program tags.

Style is the form in which to display the tag by default. The following table provides you with information on the base and notation used for each style.

Edit and Monitor Tags

To edit existing tags select the Logic > Edit Tags menu item. A spread sheet like view lets you create and edit tags.

Clicking the + sign next to a tag reveals its structure. For a DINT tag this is the 32 individual bits that make up the tag which will not be of interest if you are using the tag as a number rather then individual bits. If you do wish to use the individual bits then you can address them in this way with the tag name followed by a period and then the bit position (e.g. MyTag.5). Shown below is the expanded structure for a TIMER. Notice it is made of two DINTs and three BOOLs. In this case, the Booleans are packed into one DINT and therefore a timer uses three DINTs of memory.

An Easier Way to Create Tags

The easiest way to create tags is on the fly while programming. When an instruction is first used a “?” will indicated the need for a tag. There are three options at this point:

1. Double click on the “?” and select an existing tag from the drop down box.
2. Right click on the “?” and select new tag.
3. Double click on the “?” and type in the tag name. If it does not all ready exist, then right click on the tag name and select Create “NewTagName”. Be careful with this method not to use spaces or special characters.

The nice thing about all these methods is that RSLogix5000 will automatically fill in the correct data type according to the instruction used.

Another quick method is to drag and drop an existing tag to a new instruction. Make sure to click on the tag name rather then the instruction.

Conclusion

These are the basics of tags. The advantages are:

1. Tags, if done right, create a level of documentation that is stored in the PLC.
2. The software does an automatic housekeeping of memory locations. There’s no more worrying about physical addressing and memory conflicts.
3. Structures can be more easily put together based on function rather then data type.

Advance subjects include arrays, user defined data types (UDT) and Add-On Instructions. Hopefully, you will continue to learn more about the power of tags. There is no doubt that if you grasp the principles presented here you will be well on your way to using and troubleshooting any Logix5000 controller.

A Quick Tutorial on RSLogix Emulator 5000

RSLogix Emulator 5000 is a software simulator for the Allen Bradley line of Logix 5000 controllers (ControlLogix®, CompactLogix®, FlexLogix®, SoftLogix5800® and DriveLogix®).   The goal is to mimic the function of a PLC without the actual hardware and thus do advanced debugging.  More information can be found in the AB publication LGEM5K-GR015A-EN-P.

As a quick introduction we’ll go through a simple example of setting up a simulation.  This involves three major steps.

1. Setting up the chassis monitor.
2. Creating a connection in RSLinx.
3. Creating a project with associated emulation hardware.

Setting up the Chassis Monitor

To start the Chassis Monitor, click Start > Programs > Rockwell Software > RSLogixEmulate 5000 > RSLogix Emulate 5000 Chassis Monitor.
 

From here we set up our hardware configuration for simulation.  Our first step will be to add the CPU.  In this case it is a special one called an Emulation Controller.

1. Click Slot > Create Module.
2. Choose the Emulator RSLogix Emulate 5000 Controller.
3. Chose slot 2 for the controller
4. Click OK to add it to the chassis monitor.
   
5. At this point you may be accosted with a message about previous configurations.  Just select Reset the Configuration to Default Values and click NEXT.
6. The next two dialog screens are for setting up the controller details.  Click NEXT and FINISH to accept all the defaults.
   
   
    
   
    
    

Next we’ll add some input/output simulation.

1. Click Slot > Create Module.
2. Choose the 1789-SIM 32 Point Input/Output Simulator.
3. Chose slot 3 for the simulator and click OK.
   
   
4. Accept the defaults for the setup by clicking NEXT and FINISH.
   
   
    
   
    

The chassis monitor will now have two emulation modules in it ready to go. 

Creating a connection in RSLinx

1. Start RSLinx under Start > Programs > Rockwell Software > RSLinx > RSLinx Classic
2. Click Communications > Configure Drivers.
3. Select the Virtual Backplane (SoftLogix 58xx) driver from the Available Driver Types list.
4. Click Add New. The Add New RSLinx Driver dialog box appears. Click OK.
5. The new driver appears in the Configured Drivers list. Click Close.

Getting Started with the Logix5000 PIDE Function Block

The PIDE (Enhanced PID) is an Allen Bradley Logix5000 family (ControlLogix, CompactLogix, FlexLogix, SoftLogix) function block that improves on the standard PID found in all their controllers.  First impressions of this function block are quite intimidating.  If you try to dive into it head first you may just end up banging your head against a wall.  Many will be quite happy to stick with the tried and true PID instruction but to compete with the more advanced process control applications the PIDE boasts the following.

• It uses the velocity form of the PID algorithm.  This is especially useful for adaptive gains or multiloop selection.
• Control of the instruction can be switched between Program and Operator modes.
• Better support for cascading and ratio control.
• Built in autotuner (requires extra key)
• Support for different timing modes
• More limiting and fault handling selections.

Still interested?  What we want to do here is basically get you off the ground with the PIDE, distill all the options to the essentials and get it working.

The PIDE is only available as a function block (sorry, no ladder).  Like the PID instruction it is best to set it up in its own periodic task.  The period of the task automatically becomes the sample rate (DeltaT) of the PID loop.  Just make sure when adding the new routine to the task to select the Type as "Function Block Diagram." 

Adding the PIDE Function Block

The PIDE instruction can be added from the Instruction Toolbar under the Process tab.

Once you plop a function block onto a sheet it automatically creates a program tag for the instruction which stores all the settings.  The parameters can be set or monitored by wiring input and output references or by clicking on the ellipsis box in the top right corner to reveal the block properties. 

Opening the block properties for the PIDE instruction before RSLogix5000 version 15 meant you would be accosted with a long list of parameters.

Version 15 has at least organized some of the more common settings (but not all) under tabs and groups.
 

The most essential settings are:

Program/Operator Control

The first thing to understand when programming a PIDE block is the different controls and modes available. 

The Program/Operator control lets you transfer control of the PID loop between the user program and an operator interface such as an HMI.  Each control has separate set points and mode controls.  It's important to understand that when in Program Control the set point is determined by SPProg while in Operator Control its SPOper.  The SP output indicates the set point that the function block is actually using.

Control is determined by the following inputs:

The ProgOper output indicates the control of the PIDE instruction.  If the output is a 1 then it is in Program control and if the output is a 0 then it is in Operator control.  The Program request inputs take precedence over the Operator requests so that the program can lock out any operator overrides.  The ProgValueReset input clears all input requests.

Operating Modes

The PIDE instruction supports the following modes.

If a fault occurs in the PIDE settings then it is forced into Manual mode and sets a corresponding bit in the Status words.  The InstructFault output is the indicator of a fault.  For more detail open the block properties and look at the Status at the bottom of the dialog box.  Refer to the Logix5000 Controllers Process Control and Drives Instructions (pub 1756-RM006D-EN-P) for details.

Basic Example

Here's an example where just the essentials are used.  This is a temperature control application if you hadn't guessed all ready.  I've changed the look of the function block by going into the block properties, selecting the Parameters tab and checking on (or off) the boxes in the Vis column besides the inputs and outputs that are of concern.

Here's the run down on each of the inputs.

Now for the outputs.

Common Problems

Conclusion

Hopefully this basic introduction has gotten you off the ground.  Half the battle is just getting it to work.  Once that is done you can now really start to tinker with the power of the PIDE function block.

Further Reference

• Logix5000 Controllers Process Control and Drives Instructions (Publication 1756-RM006D-EN-P)
• Using the PIDE Instruction (Publication LOGIX-WP008A-EN-P - August 2005)
• Using a Logix Controller for Barrel Temperature Control on Plastic Injection Molding and Extruding Machines (Publication RA-AP015A-EN-P €“ February, 2004)

Install and Test a MVI46-MCM Modbus Module for SLC-500

by Nugroho Budi from controlmanuals.com

The MVI46-MCM is a Modbus communication module provided by ProSoft Technology. The module can be installed in a SLC500 rack so it can communicate to other Modbus devices.

This article assumes you have an Allen Bradley SLC 5/03, 5/04, or 5/05 processor with a power supply of adequate capacity for the MVI46-MCM plus any Input/Output (I/O) modules you intend to use.  For the purposes of this lab, and to match the supplied sample ladder, we will assume a configuration as follows:

• A-B 1747-L551 5/05Processor – 16K Memory, OS500
• A-B 1746-A7 7-Slot Chassis (rack)
• A-B 1746-P1/P7 Power Supply

If different hardware is used, modifications to the sample ladder file, MVI46MCM.RSS will need to be made to obtain a properly functioning program.

Installing the Module

1. Before installing the MVI46-MCM into the SLC chassis, check the position of the Interface Configuration Jumpers on the bottom of the module.
   
   
   
   The Setup Jumper is only necessary when used to flash a firmware upgrade onto the module.  For normal configuration and operation, this jumper must be positioned as shown in the diagram above.  We will be using the RS-232 interface, so check that the PRT2 and PRT3 jumpers are positioned as shown above so the module will communicate in RS-232 mode.
2. NOTE:  For this step, and at any time when you are installing or removing hardware to or from the chassis, you MUST do so with the POWER OFF!  SLC modules are NOT HOT SWAPABLE.  Attempting to insert or remove modules while the chassis is powered-up can result in damage to the module, the processor, the Power Supply, and/or the Chassis itself!
   
   Chassis slots are numbered sequentially, left to right, starting at zero for the leftmost slot.  The processor always goes in Slot 0.  Install the MVI46-MCM module into the slot next to the processor.  This will place the module in Slot 1.  The rest of the chassis slots should be left empty, for now.  If done correctly, your installation should look similar to the following illustration:
   
   
   
3. Set the processor key switch to the REM position and power up the chassis.
   
   After its boot cycle, the processor will be ready to accept programming. At this point, you may ignore any RED LEDs indicating processor or module faults.  Until a valid project (program) is loaded into the processor it may show a fault.

Configure RSLinx to Talk to SLC

1. Attach a null modem cable (or the A-B CP3 programming cable) from your PC serial port to the serial port on your SLC processor, called Channel 0.
2. Open RSLinx.  Click on the “Communications” drop-down menu.  Click on the “Configure Drivers” option.  If you’re running a newer version of RSLinx, you’ll see a dialog box like this one:
   
   
   
   If you already have a RS-232 DF-1 driver configured, skip to the Auto Configure instructions in Step 5.
3. Click the down arrow in the “Available Driver Types:” option box and click on “RS-232 DF-1 devices”, as shown, and click the “Add New…” button.
   
   
4. You will now be prompted to name your driver.  For most cases, the default name will be acceptable.  To match the sample project used in this lab, accept the default name by clicking the “OK” button.
   
   
5. Next, you will see the driver setup dialog box.
1. First, click the down arrow in the “Comm Port:” option box and click the Comm port that matches the number on your PC (usually Comm1, Comm2, Comm3, or Comm4). 
2. Then, click the down arrow in the “Devices:” option box and click the “SLC-CH0/Micro/PanelView” option. 
3. Finally, click the “Auto Configure” button.  RSLinx will then query the processor, establish a communications link, and adjust the driver’s parameters to match the processor’s current port configuration. Don’t worry if the parameters in your driver don’t match the ones shown in the following example.  As long as the window reports “Auto Configuration Successful!”, whatever parameters appear for baud rate, parity, error checking, etc. will be correct.  A successful result will look something like this:
   
   
   
   In some instances, RSLinx will fail to Auto Configure.  If this happens to you, first check that your cable is OK, properly connected, and that you are selecting the correct Comm port.  Once this is verified, if Auto Configure fails, you will need to completely wipe the processor memory and reset it to factory defaults.  Consult the A-B product documentation, the A-B website, or A-B Tech Support for instruction on how to do this. Once done, the RSLinx should be able to Auto Configure.
   
   Clicking on “OK” will return you to this dialog:
    
   If the driver status is “Running”,  you have now successfully configured RSLinx to talk to the processor.  Click the “Close” button to close this dialog and then exit but do not shutdown RSLinx by clicking the “File” menu option and then “Exit and Shutdown”. Be sure to click the “Exit” option.

Use RSLogix500 to Modify the Sample Project

1. Next, we will load and configure the sample ladder logic program and download it to the processor. Start RSLogix500.  It should come up to a blank window, like this:
   
   
2. Click on the “File” drop-down menu, click “Open” and browse to the folder where you saved the sample ladder and double-click the file, “MVI46MCM.RSS” that is included on the MVI46MCM CD.
   
   
   
   This will open the sample project.  We can now configure the sample ladder to get it ready for the next exercise.
3. You’ll get a window that looks like this.  If not, then click on the “View” Menu, and make sure there are check marks beside “Standard”, “Online”, and “Tabbed Instruction Bar” options.
   
   
4. In the left pane Project Tree area, under the Controller folder, double-click on the “IO Configuration” icon.  This will display the I/O Configuration dialog box:
   
   
5. Click on “OTHER” in Slot 1, as shown, then click the “Adv Config” button.
   
   
   
   Make sure the values are as shown.  If they are not, set them to these values. Otherwise, the module will not function properly.  Details on module setup are contained in the User’s Manual in Section 3.3 “Setting Up the Module”.  After you verify the values, click “OK” or “Cancel” to close this dialog box.  Click on the Exit icon () in the upper-right corner of the I/O Configuration dialog to close it and return to the main window.
6. In the left pane Project Tree area, under the Data Files folder, double-click on the N10 – MCM CFG icon.  Set the values in this file to match the ones shown below.
   
   
   
   

   MCM Ports 1 & 2 Cmds

   Port 1 / Port 2

   -  N10:10 / N10:40  Port Enable/Disable

   -  N10:11 / N10:41  Port Type

   -  N10:12 / N10:42  Float Flag

   -  N10:13 / N10:43  Float Start

   -  N10:14 / N10:44  Float Offset

   -  N10:15 / N10:45  Protocol

   -  N10:16 / N10:46  Baud Rate

   -  N10:17 / N10:47  Parity

   -  N10:18 / N10:48  Data Bits

   -  N10:19 / N10:49  Stop Bits

   -  N10:20 / N10:50  RTS On Delay

   -  N10:21 / N10:51  RTS Off Delay

   -  N10:22 / N10:52  Min. Response Delay

   -  N10:23 / N10:53  Use CTS Line

   -  N10:24 / N10:54  Slave ID

   -  N10:25 / N10:55  Bit Input Offset

   -  N10:26 / N10:56  Word Input Offset

   -  N10:27 / N10:57  Output Offset

   -  N10:28 / N10:58  Holding Register Offset

   -  N10:29 / N10:59  Command Count

   -  N10:30 / N10:60  Min. Command Delay

   -  N10:31 / N10:61  Command Error Pointer

   -  N10:32 / N10:62  Response Timeout

   -  N10:33 / N10:63  Retry Count

   -  N10:34 / N10:64  Error Delay Count

   -  N10:35 / N10:65  Reserved

   -  N10:36 / N10:66  Guard Band

   -  N10:37 / N10:67  Guard Band Timeout

   
   This configuration data will set module Port1 to be a Modbus Master and Port2 to be a Modbus Slave.  Both ports will be set for Modbus RTU mode, 57,600-baud, no parity, 8 data bits, 1 stop bit.  Hardware handshaking will be disabled (RTS/CTS not used.)  We will be able to use up to 5 Modbus Commands and any Modbus Command Errors will be sent to module memory beginning at register address 300, which will then appear in SLC data table N31, beginning at N31:100.  With this configuration, we can use a second null modem
   cable and two DB9M-to-RJ45 pigtails to connect the two ports together, which in turn will allow us to send and get data from the module with our sample ladder.  Click on the Exit icon () in the upper-right corner of the Data File N10(dec) dialog to close it and return to the main window.

7. We will now configure our Modbus commands for Port1.  In the left pane Project Tree area, under the Data Files folder, double-click on the N11 – P1 CMDS icon.  Set the values in this file to match the ones shown below.
   
   
   
   

   MCM Ports 1 & 2 Cmds

   Port 1 / Port 2

   -  N11:0 / N12:0  Cmd Enable

   -  N11:1 / N12:1  Internal Address

   -  N11:2 / N12:2  Poll Interval Time

   -  N11:3 / N12:3  Count

   -  N11:4 / N12:4  Swap Code

   -  N11:5 / N12:5  Node Address Device ID

   -  N11:6 / N12:6  Function Code

   -  N11:7 / N12:7  Device Address Register

   
   This creates one Modbus command for Port1, our Master port.  This command will send a request out Port1 to the Modbus Slave at Slave ID 2 (our Port2), as configured in N10.  The command will get twenty 16-bit words (registers) of data from Destination Address 0, our module address 0, the first word of our WRITE DATA area, and move it out Port2, in Port1, and store it in Internal Address 200, our module address 200, the first word of our READ DATA area.  This command will execute once each second.  This way, any values we poke into data table addresses N32:0 through N32:19 will, after a short delay, appear in the corresponding addresses in data table N31. Click on the Exit icon () in the upper-right corner of the Data File N11 (dec) dialog to close it and return to the main window.

8. In the left pane Project Tree area, under the Data Files folder, double-click on the N12 – P2 CMDS icon.  Set all the values in this file to zero and click on the Exit icon () in the upper-right corner to close this window and return.
9. In the left pane Project Tree area, under the Data Files folder, double-click on the N32 – WRITE DATA icon.  Set the values in this file as shown.
   
   
   
   This will give us some beginning data values for the Modbus command we just created.  Click on the Exit icon () it the upper-right corner to close this window and return.
10. In the left pane Project Tree area, under the Data Files folder, double-click on the N31 – READ DATA icon. Set the values in this file to zero so that we will know that any values that appear there are the result of our ladder logic execution.  Click on the Exit icon () in the upper-right corner to close this window and return.
11. We are now ready to save our new project before downloading.  In the main window, click on “File”, then “Save As” to get the Save As dialog box.  In the File Name: box, type “46Test1”, as shown, and click the Save button.
    
    

Congratulations!  You now have a functioning program that will move data to and from the module.

Downloading and Testing the Modified Sample Project

1. Make sure your null modem cable (or CP3 programming cable) is still attached between your PC Comm port and the processor RS-232 port.  Take the two DB9M-to-RJ45 pigtails and the other null modem cable and connect the lower two ports on the MVI46MCM module,
   P2 APPLICATION and P3 APPLICATION, with these cables.
2. Set the processor key switch to the “PROG” position.  In RSLogix500, click the down-arrow next to the “OFFLINE” status and click “Download…” from the menu.
   
   
   
   When you see the confirmation dialog, click the “Yes” button.
   
   
   
   The sample ladder is currently configured for a 1747-L551 SLC 5/05.  If you are using a different processor, when you try to download, you will see the following:
   
   
   
   If you get this warning screen, click the “OK” button.  RSLogix will automatically determine the actual processor type you are using and adjust the IO Configuration to match your installed processor.  You should then see the following window:
   
   
   
   When it comes up, make sure the “Clear I/O” box is NOT checked, as shown, and click “OK”.  A Download Progress dialog will flash through several progress bars as various parts of the program are loaded.  Eventually, you should see:
   
   
   
   Click the “Yes” button.  The RSLogix status box will change to show you are on-line live with the processor.  You can also tell you are on-line when you see the colored blocks and ladder rotating in the status box.  The faster they rotate, the higher your connection speed.  It should look like this (with animated ladder):
   
   
   
   If you had to change your processor type, now would be a good time to re-save the program.
3. Next, we will change the SLC 500 processor key switch from “PROG” to “RUN” and back to the “REM” position.  If you have a good program, the processor RUN LED will light up solid green and, on the MVI46MCM module, the OK LED will change from red to green, the APP STATUS and BP ACT LEDs will be amber and the LEDs for P2 and P3 will flash green about once every second.  The RSLogix status box should look like this:
   
   
   
   If, however, the processor “FAULT” LED flashes red and you see this,
   
   
   
   it indicates some kind of hardware or software problem.  Common causes include: hardware failure, ladder logic errors, and installing the MVI46MCM module in a different chassis slot than the one selected in the I/O Configuration, I/O modules in the configuration that are not actually installed in the chassis, and more.  Assuming you are still on-line with the processor, to see what might be causing the problem, you can check the “Processor Status” dialog for the Major Error Code causing the fault.  In the Project Tree, under the
   “Controller” folder, click on “Processor Status” then click on the “Errors” tab to see the fault.  An example of having the module in the wrong slot is shown. Your error may be different.
   
   
   
   Do whatever is required to fix the root cause of the fault and then turn the key switch from “REM” to “PROG” to “RUN” and back to “REM” to get the processor running normally.
4. NOW…We’re ready for some real fun.  Take a few minutes to look at the three LAD files in our test program.  For a detailed explanation of what these files do, look at Chapter 4 – Ladder Logic in the User’s Manual, beginning on page 25.
   
   Now, look in LAD 4 –MCM CMDS at rungs 0002 and 0003.  Bit B3:0/0 in rung 0002 is called the Cold Boot bit.  Bit B3:0/1 in rung 0003 is called the Warm Boot bit.  Either may be toggled to force the module to restart, reload its configuration and any Modbus commands.  This is a handy feature that makes it easy to change and test different configurations and commands.  It’s quicker and safer to toggle these bits than to recycle the processor or power-down and power-up the chassis to accomplish the same thing.  Toggling either of these bits allows configuration and command changes to be performed without halting the processor.  This can be very useful when added one of our modules to an existing application already in use at a customer site.  As we progress through the rest of this exercise, we will be returning to this ladder and these rungs often as we modify and test our program.
   
   Toggle one of these bits now and watch the LEDs on the front of the module as you do so.  You should see the P2 and P3 LEDs stop the regular blinking they had been doing, the OK LED will briefly turn red then go back to green, and then the P2 and P3 LEDs should resume their blinking once a second.
   
   To toggle the bit, right-click on its picture then click on “Toggle Bit” at the bottom of the context menu, as shown.  Be sure to watch the face of the MVI46-MCM module as you click.
   
   
5. Now we can check to be sure our program is moving the data as it should.  Remember previously that we zeroed out our READ DATA table and put test values in our WRITE DATA table.  If our program is working correctly, we should now have the same values in the same relative addresses in our READ DATA as in the WRITE DATA.  First, let’s check the WRITE DATA table to be sure our test values are still there. In the Project Tree, under the Data Files folder, double-click “N32 – WRITE DATA”.
   
   
   
   Yep!  Our test data is still there, just the way we left it.  Now, for the moment of truth…does our N31 – READ DATA table look the same?
6. Double-click on “N31 – READ DATA” and let’s see.  If your tables overlap each other, you can click-and-hold on the blue Title Bar of either one, drag it to a different position in the window, and release.  Ready, GO!
   
   
   
   YES!!!!!  They MATCH!  Now, that was easy, wasn’t it?  You can experiment further with the above by changing the values in Data File 32, N32:0 through N32:19. With the PLC in Run Mode the values in Date File 31, N31:0 through N31:19 should, after a very short delay match those in Data File 32.

Using ModScan to simulate the Modbus Master

1. Using Windows File Explorer, go to the CD and expand the yellow folder in the left side tree pane titled Utilities under the InRAx folder until you see a folder titled Modscan.
   
   
2. Double-click on the compressed folder in the right side Explorer pane to extract its contents.  Choose or create a new folder to contain these files.  A suggestion would be to create a new folder titled Modscan, and then extract the compressed files into this new folder.
3. After extracting the Modscan files, locate and double-click on the file titled Modscan.exe.  You should see the following program appear.
   
4. This is the Windows program called Modscan.  This is a shareware program and can be used for 30 days, after which you are asked to purchase it.
5. To use the program, click either Cancel or OK to close out the “Registration Information” dialog window. You may have to click once inside the window, and then click OK. Repeat if necessary. Now we are ready to use the program.
6. Remove the short RJ45 pigtail cable from Port 1 on the MVI46-MCM and then disconnect it from the RS232 Null Modem cable.  Now connect the RS232 Null Modem cable directly to the COM 1 port on your computer.  If you currently have another cable connected to
   your computer’s COM 1 port for interfacing to the SLC-500, first go offline with RSLogix 500 software, then disconnect that cable and connect the RS232 Null Modem cable that was previously connected to Port 1 of the MVI46-MCM module. We should now have COM1 on our PC connected with a RS232 Null Modem cable directly to Port 2 on our MVI46-MCM module which is configured as a Modbus Slave device.
7. In the Modscan program, click on the menu choice called “Setup”, and then click on Serial. Configure the settings as shown below. Click OK when done.
   
   
8. Now click Setup, then Display and make sure that Data and Decimal have check marks beside them. Click on Setup, then Protocol and make sure RTU is checked also.
9. Now configure the main window as below.
   
   
10. Now click on the menu item “Action”, then Start Poll.  You may have to clear a popup window first, but you should see results like below which shows our original data that was in our Data File 32.
    
    

    
    The register addresses are on the left and listed 40001 through 40020 and each registers value is directly to the right of it.

Congratulations, you have just used a Windows software program called Modscan acting as a Modbus Master device to go out and read data from our MVI46-MCM module’s Port 2 which is a Modbus Slave device.

NOTE : Based on my experience the MVIMCM for SLC500 is unable to be a Slave and must be A MASTER  to communicate with other Modbus PLC/Devices (Scadapack32, Micromotion, UltraSonic Flow Meter GM868..)

Learn Ladder Logic with a Free Version of RSLogix 500 and RSEmulator 500

One of my most common questions is, “Where can I get a free download of RSLogix 500?”  For any serious development with SLC500 or MicroLogix there is no free option but there is a nice free option if you only want to learn and/or program a MicroLogix 1000 or 1100.  Programming a MicroLogix is very very similar to programming a SLC500 or in that case a PLC5 too. 

Allen Bradley offers as a free download a software package called RSLogix Micro Starter Lite which is essentially the same programming environment as RSLogix 500.  On top of that, they also offer RSLogix Emulate for free so that you don’t even need a PLC to run and test your ladder logic.  Keep reading and I’ll show you how to get the software and set it up.

Getting the Software

The RSLogix Micro Starter Lite software is only available as a download at http://www.ab.com/programmablecontrol/plc/micrologix/downloads.html.  If you are starting from scratch and do not have the RSLinx software then download the kit bundled with RSLinx Classic Lite.  FYI, I find it a bit confusing but they also sell software called RSLogix Micro Starter which supports the full MicroLogix range.

If you do not have a MicroLogix 1000 or 1100 to play with then download the RSLogix Emulate 500 software.  You’ll be able to use this to simulate a real PLC.

Note for Windows XP users:  The bundled version of RSLinx only installs on Windows Pro and is not supported on Windows XP Home versions.  To get around this I downloaded an older version of RSLinx Lite 2.50 from the Allen Bradley software update page http://www.rockwellautomation.com/support/webupdates/

Once you’ve downloaded the software and extracted it then install RSLogix Micro followed by the RSLinx Classic Lite software.  Next, install the RSLogix Emulate 500 software.

First Steps with RSLinx

RSLinx is the software RSLogix will use to communicate with your PLC or in our case to the emulator.

Let’s start by running the RSLinx software under the START > All Programs > Rockwell Software > RSLinx > RSLinx Classic shortcut.  Follow these steps to set it up:

1. Under the Communications menu select Configure Drivers.   
2. Under the Available Drivers Types select the “SLC 500 (DH485) Emulator driver” and click the Add New… button. 
3. You can give the driver a name but I just leave it at the default of EMU500-1. 
4. Leave the configuration options as Station Number 00 and click OK.

Your driver should now be running and look like the picture below.

Ok, that’s ready to go.  Close the Configure Drivers dialog box and close RSLinx.  Actually RSLinx is now running in the background and you’ll probably see its little icon in the system tray.

RSLogix Micro Starter Lite

Now for the moment we’ve all been waiting for--- creating some ladder logic.  Open the RSLogix Micro software with the START > All Programs > Rockwell Software > RSLogix Micro English > RSLogix Micro English shortcut.  Create a brand new project by pulling down the File menu and selecting New.  Every project must start with a designated processor. 

In my case I’ve chosen the simplest MicroLogix 1000 and then clicked the OK button.  FYI, if you ever work with the purchased version of RSLogix 500 then there will be a lot more items in this hardware list.  A blank project now opens up.

Let’s make a simple rung to test in our emulator.  Make sure the cursor is on the rung with the END on it and then click the New Rung icon in the instruction toolbar.

Now click on the “Examine if Closed”  instruction to add it to the rung.  Double click on the question mark above it and enter I:0/0 as its input address.  Just leave the description pop up box empty by clicking OK.

Next, click on the Output Energize  instruction to add it to the right side of the rung.  Double click on the question mark above it and enter O:0/0 as its output address.  Just leave the description pop up box empty by clicking OK.

You should now have something like below.

The next very important step is to verify the project with the Edit > Verify Project menu item.  This will compile the project and get it ready for the emulator.

Save the project as something like Test.RSS in an easy place to find like My Documents.

RSEmulator 500

The emulator lets us test our work by running a virtual PLC.  We’ll be able to download our program to it and run it in a very similar fashion to a real PLC.  Start the emulator with the START > All Programs > Rockwell Software > RSLogix Emulate 500 > RSLogix Emulate 500 shortcut.   The emulator is pictured below.  I know.  It doesn’t look like much but it gets the job done.

Select File > Open and open the RSLogix project you created earlier (I named mine TEST.RSS).  In the dialog box that pops up put the Station # as 1 and click Ok.

Believe it or not but the emulator is now ready.  Leave it running and go back to your project in RSLogix Micro.

Testing the Ladder Logic

In RSLogix Micro Starter select the Comms > System Comms menu item.  The following dialog box will pop up.

In the left hand pane, drill down and select the “01, MicroLogix 1000, TEST” processor.  Yours might look a little different if you selected different hardware or gave the processor a different name.  For good measure make sure Apply to Project is checked and then click on Download.  When prompted to go Online click on Yes.

If successful you’ll see the ladder picture spinning round on the online toolbar.  To scan the ladder logic put the processor into Run mode by clicking on the arrow to the right of mode status (REMOTE PROGRAM).

To test the ladder logic, change the input state by right clicking on the address and selecting toggle bit.

You will see the instruction go green indicating it is true and it will make the output instruction turn green also indicating the output is turned on.

That’s it!  You get all that for the cost of a download.  Now break out the manuals and start learning about all the different instructions.

RSLogix 5000 Tips and Tricks

Everybody enjoys nifty little tips and tricks to get their work done faster. This listing is for Allen Bradley's RSLogix 5000 software. Feel free to add your own tips and tricks using the 'add comment' link.

The Logix5000 Essential Manuals

The Allen Bradley Logix5000 family (ControlLogix, CompactLogix, FlexLogix, SoftLogix) has some very good manuals. If you are just starting out or need a refresher here are the key manuals and the order I would read them. If you have RSLogix 50000 installed then you will find some of these in the Help > Online Books menu. Revision 16 also has some great videos in the Learning Center.

The Basics

For starters there is the Quick Start manual.
Logix5000 Controllers Quick Start

The Essentials

If you are getting into programming and designing a system then you'll want to start off with the Common Procedure Manual. It has a lot of helpful examples dealing with all aspects of the system.
Logix5000 Controllers Common Procedures Programming Manual

Next comes the nitty gritty of each instruction. It's a good idea to at least peruse all the instructions so you have an idea of what is available.
Logix5000 Controllers General Instructions Reference Manual
Logix5000 Process Control and Drives Instructions Reference Manual
Logix5000 Controllers Motion Instructions
GuardLogix Safety Application Instruction Set Reference Manual

An often overlooked manual but filled with great information for getting the most out your designs is the Design Considerations Reference Manual. Certainly a must read if you are knee deep in the development and programming of Allen Bradley PLCs.
Logix5000 Controllers Design Considerations Reference Manual

Hardware Specifics

Specifics for the hardware can be found in the User Manuals and Installation Instructions for the PLC.

ControlLogix
ControlLogix System User Manual
ControlLogix Installation Instructions
ControlLogix Controller and Memory Board Installation Instructions

CompactLogix
CompactLogix System User Manual
CompactLogix 1769-L20, 1769-L30 Installation Instructions
CompactLogix 1769-L32E, 1769-L35E Installation Instructions
CompactLogix 1769-L32C, 1769-L35CR Installation Instructions

FlexLogix
FlexLogix System User Manual
FlexLogix Controllers Installation Instructions

SoftLogix
SoftLogix System User Manual
SoftLogix Controllers Installation Instructions

GuardLogix
GuardLogix Controllers User Manual
GuardLogix Controllers Installation Instructions

Networking

If you are deciding on which network to use then see the Design Considerations manual and the section "Determine the Appropriate Network". Otherwise, for existing networks the following are helpful.

Ethernet/IP
Ethernet Design Considerations for Control System Networks
EtherNet/IP Modules in Logix5000 Control Systems User Manual
Guard I/O EtherNet/IP Safety Modules User Manual

ControlNet
ControlNet Modules in Logix5000 Control Systems

DeviceNet
DeviceNet Modules in Logix5000 Control Systems User Manual
Guard I/O DeviceNet Safety Modules

The links are from the AB site so they are the latest and greatest manuals. Let me know if any of them are broken or if I forgot one you think is essential.

User Defined Data Types (UDTs) and OOP

by John Schop

For years now, Object Oriented Programming paradigm (or OOP) has been a commonly used programming practice, and has of course found its way into industrial automation as well.

In the mean time, most PLC manufacturers have found ways to make the programmers life easier by introducing User Defined Types or UDTs. The name says it all; it is a ‘type’ that you, the programmer, can define all by yourself. This means that your programming environment will not only have the regular integers (INT) and Booleans (BOOL), but could also have a ‘VALVE’ type or a ‘MOTOR’ type.

I can’t speak for other brands of PLC’s, but the Allen Bradley ControlLogix series of PLC’s, together with RSLogix 5000 programming software, makes it very easy to work with these UDTs, and since the introduction of RSLogix version 17 earlier this year, it is now even possible to edit your UDTs while online with a running system.

The Controller Organizer has a folder called Data Types > User-Defined with all the UDTs in the project.

I am of the opinion that every PLC program should rely heavily on UDTs to improve readability, and if you are an OOP adept, it can be a great help to organize your classes.

Let’s go over the fundamentals of OOP for a little bit:

• Classes: Classes define the abstract characteristics and behavior of an object. For example, a simple ‘VALVE’ class would have the characteristics (or attributes) that it can be open or closed (the things it can be), and as far as behavior goes, it could have the methods ‘to open’ and ‘to close’ (the things it can do)
• Objects: An object is an instance (occurrence) of a class. In our example, there could be a Valve_001 and a Valve_002, which are both instances of the class ‘VALVE’, with the same attributes and methods.

Of course the definition of OOP goes a lot further than this. There is a very understandable explanation here: http://en.wikipedia.org/wiki/Object-oriented_programming#Fundamental_concepts for those who would like to read more. For now, let’s leave it at this, and see how we can apply this to an industrial environment.

If you look at a valve as an object in a typical industrial automation environment, you should note the following:

• It has inputs and outputs that are specific for the object (proximity switches and solenoids).
• It can be either ‘open’ or ‘closed’
• You can tell it to go ‘open’ or ‘close’.
• It could have an alarm timer, that would tell us if the valve did not open or close in a given time period after a command.
• It might have interlocks, which allow the valve to open or close under certain conditions.

A UDT for this class, would fit all these properties and methods in one simple type. But, as always, we can expect further complications of the class ‘VALVE’ during the realization of a project. To be as flexible as possible, I highly recommend the practice of nesting UDT’s, which will become clear along the way.

Let’s start with defining our class, and keep in mind that it will have to be easily accessible for maintenance people or other programmers.

If we start at the I/O end, the best method is to create sub-classes called VALVE_IN and VALVE_OUT, which will contain our I/O.

The following example uses RSLogix5000 V16. First, create the sub-classes. From the File menu select New Component > Tag. The following dialog box appears to create and edit the members of the UDT.

Now, make a UDT called VALVE, and ‘nest’ these sub-UDTs in it:

As you see, I am allowed to take the types I just created as the data type in this UDT. The real advantage of this feature will become clear if you create a object called Valve001 of the type VALVE, and look at the object in the ‘monitor tags’ window:

Wow! Just by creating a new tag of the type VALVE, it gets all these I/O points right away, and referenced in the program:

Of course, going further with this concept, everything for a valve can be included in one object. Allow me to skip some steps, and show you a possible final result:

The ‘VALVE’ class is now contained in a UDT called VALVE, which looks like this:

As you see, the class VALVE now consists of the sub-classes VALVE_IN, VALVE_OUT, VALVE_TIMER, VALVE_STATUS, etc.

And an instance of this class, the object Valve001, would look like this:

While adding stuff to my class, I did not have to re-create the object Valve001. RSLogix updated it for me, so all the properties and methods are available in my program.

Now, let’s say you’re working on this project with a couple hundred valves, and the customer decides to go with a different type of valve, that also has an analog input, that tells us the exact position of the valve. All we have to do is modify our VALVE_IN sub-class to add this to every instance of the type VALVE:

Of course, you would still have to write code to tell your program what to do with that information, but that is also the reason why PLC programmers still have a job.

For somebody that is not familiar with your program, it might be confusing to look at all your UDT’s. We just made eight UDT’s for one simple valve class! But remember, you only have to do this during the design phase. Once you have a solid design for all your classes (and made sure their names are self-explanatory), you will never have to look at your UDT folder again, and creating a new instance will be a breeze.

Connecting Excel to ControlLogix

by John Schop

Have you ever lost data in a CLX processor, because you downloaded new code? Unfortunately, when you donwload a program to a ControlLogix processor, you also download the values of the tags (variables).

A solution to this problem that could be useful, is an Excel sheet that reads and writes values to the ControlLogix processor using the DDE/OPC capabilities of RSLinx.

In this article, I will show you how to create one of these sheets for your projects.

Here's what you'll need:

• Microsoft Excel, with some basic knowledge about programming macro's in Visual Basic
• RSLinx (not the 'Lite' version, because that does not have DDE/OPC capabilities)
• A ControlLogix processor of course

Let's fire up RSLogix first, and create a bunch of tags with values. In this example, I created 2 arrays, of the types DINT and REAL, each with a length of [10] tags. These arrays I filled with some values:

I'm not going to do anything with the PLC program, I just need some data in a number of tags.

Next, we're going to set up a DDE/OPC Topic in RSLinx. Depending on the version of RSLinx you use, it might look slightly different, but you should be able to follw this with the screenshots.

Assuming that you know how to setup RSLinx initally to get online with your controller, I've skipped some steps. The setup I use looks like this in RSLinx:

As you can see, I have a 10 slot CLX rack, with a 1756-ENBT card in slot 1 (address 134.200.211.16), and two processors, one in slot 0, and one in slot 2. The one in slot 2 is the processor we are going to use for this exercise.

Now, open up the DDE/OPC topic configuration by clicking 'DDE/OPC' and then 'Topic Configuration' in the top menu of RSLinx.

I'm going to create a new DDE/OPC topic called 'EXCEL_TEST', and use the Logix5550 processor in slot 2 as the data source. In order to do this, you have to click the 'New' button, give the topic the desired name, and make sure the processor in slot 2 is selected as the source before you click 'Done'

To test if your setup is working, at this point you can use the OPC test client provided with RSLinx. I'm not going into detail about that, but I did make sure this worked before continuing with the next step, creating the Excel sheet.

Let's start up good old Excel, and create a new workbook. On this workbook, place a new command button. You can find the Command Button control in the 'Control Toolbox' toolbar in Excel. When you have the button, right click on it and choose 'View Code'. This will take you to the Visual Basic Editor:

First, create a function that will open the DDE topic to Excel:

Now, if I call this function from the CommandButton1_Click event, it will open the link to RSLinx:

The variable 'rslinx' will hold the number of the open channel. All subsequent DDE functions use this number to specify the channel.

To save you all the steps to program the rest of the code, here is the final code to get the array of REALs out of the controller, and put them in cells D2 – D11, and the array of DINTs in cells E2-E11.

Now we know how to read, it would of course be a lot of fun if we could write values as well. I would like to be able to change the values in the cells, and then hit a 'Write Data' button.

First, make another button on the sheet (mine looks like below now)

And then write some code for the button:

The way this is implemented is of course very rudimentary, but once you get the concept, the sky is the limit.

To make this easier on everybody, I've included the Excel file with the code already in it. The only thing you have to do to make this Excel sheet work, is make sure there is an DDE/OPC topic in your RSLinx setup called 'EXCEL_TEST', and the arrays REAL_Array and DINT_Array in your controller (of at least length 10).