Programming Manual Logix5000 Controllers Sequential Function Charts Catalog Numbers 1756 ControlLogix, 1769 CompactLogix, 1789 SoftLogix, 1794 FlexLogix, PowerFlex 700S with DriveLogix
Important user information Read this document and the documents listed in the additional resources section about installation, configuration, and operation of this equipment before you install, configure, operate, or maintain this product. Users are required to familiarize themselves with installation and wiring instructions in addition to requirements of all applicable codes, laws, and standards.
Summary of changes This manual contains new and updated information. The following table contains the changes made to this revision. Change Topic Updated graphics and text for version 24 and Windows 7. Throughout the manual.
Table of contents Preface Studio 5000 environment...........................................................................................9 Additional resources.................................................................................................. 10 Chapter 1 Design a sequential function chart Introduction................................................................................................................ 11 What is a sequential function chart?....................................
Table of contents End the SFC ................................................................................................................ 45 Use a stop element ............................................................................................. 45 Restart (reset) the SFC ..................................................................................... 46 SFC_STOP structure ....................................................................................... 47 Nest an SFC ..............
Table of contents Document an SFC ..................................................................................................... 70 Language switching............................................................................................ 70 Add structured text comments ....................................................................... 71 Add a tag description......................................................................................... 72 Add a text box .........................
Preface This manual shows how to design and program Sequential Function Charts (SFCs) for Logix5000 controllers to execute. This manual is one of a set of related manuals that show common procedures for programming and operating Logix5000 controllers. For a complete list of common procedures manuals, refer to the Logix5000 Controllers Common Procedures Programming Manual, publication 1756-PM001. The term Logix5000 controller refers to any controller that is based on the Logix5000 operating system.
Preface Additional resources These documents contain additional information concerning related Rockwell Automation products. Resource Description Logix5000 Controllers Program Parameters Programming Manual, publication 1756-PM021 Describes how to use program parameters when programming Logix5000 controllers. Logix5000 Controllers General Instructions Reference Manual, publication 1756-RM003 Describes the available instructions for a Logix5000 controller.
Chapter 1 Design a sequential function chart Introduction A sequential function chart (SFC) is similar to a flowchart of your process. It defines the steps or states through which your system progresses. It helps you do the following: • Organize the functional specification for your system. • Program and control your system as a series of steps and transitions. By using an SFC to specify your process, you gain these advantages.
Chapter 1 Design a sequential function chart What is a sequential function chart? A sequential function chart (SFC) is similar to a flowchart. It uses steps and transitions to perform specific operations or actions. This example shows the elements of an SFC. The SFC continues on the following page. A step represents a major function of your process. It contains the actions that occur at a particular time, phase, or station. An action is one of the functions that a step performs.
Design a sequential function chart Chapter 1 A selection branch chooses between different execution paths. A text box lets you add descriptive text or notes to your SFC.
Chapter 1 Design a sequential function chart A stop lets you stop and wait for a command to restart. A wire connects one element to another element anywhere on the chart. This wire takes you to the conveyor step on the first part of this SFC (previous figure). Follow these steps to design a sequential function chart. 1. Define the tasks on page 14 2. Choose how to execute the SFC on page 15 3. Define the steps of the process on page 16 4. Organize the steps on page 20 5.
Design a sequential function chart Chapter 1 1. Organize your project. These functions Go into this type of task • Configure and regulate devices Periodic task • Command a device to a specific state SFC in the continuous task • Sequence the execution of your process 2. For those functions that go in a periodic task, group the functions according to similar update rates. Create a periodic task for each update rate. For example, 2-state devices may require faster updates than PID loops.
Chapter 1 Design a sequential function chart If Then • The SFC is the only routine in the program Configure the SFC as the main routine for the program. • The SFC calls all the other routines of the program • The program requires other routines to execute independent of the SFC 1. Configure another routine as the main routine for the program. • The SFC uses Boolean actions 2. Use the main routine to call the SFC as a subroutine.
Design a sequential function chart • Chapter 1 When you first open an SFC routine, it contains an initial step and transition. Use this step to initialize your process. The controller executes the initial step in these situations. • After a project download when the controller goes into Run mode. • When the controller transitions to Run mode and on power-up (if the SFC is configured for that).
Chapter 1 Design a sequential function chart If you want to Data type Details Determine how long a step has been active T (milliseconds) DINT When a step becomes active, the Timer (T) value resets and then starts to count up in milliseconds. The Timer continues to count up until the step goes inactive, regardless of the Preset (PRE) value. Set a flag when the step has been active for PRE a specific length of time (milliseconds) DINT Enter the time in the Preset (PRE) member.
Design a sequential function chart Chapter 1 If you want to Then select or set this member Data type Details Do something one time when the step becomes active FS1 BOOL The FS bit is on during the first scan of the step. Typically, we recommend that you use an action with a P1 Pulse (Rising Edge) qualifier to accomplish this.
Chapter 1 Design a sequential function chart This diagram shows the relationship of the X, FS, SA, and LS bits. Organize the steps Once you define the steps of your process, organize them into sequences, simultaneous branches, selection branches, or loops. To Use this structure With these considerations Execute 1 or more steps in sequence Sequence on page 22 The SFC checks the transition at the end of the step. • One executes repeatedly • If TRUE the SFC goes to the next step.
Design a sequential function chart Chapter 1 To Use this structure With these considerations Loop back to a previous step Wire to a previous step on page 24 • Connect the wire to the step or simultaneous branch to which you want to go. • Do not wire into, out of, or between a simultaneous branch. Here are some examples of SFC structures for different situations. Example situation Example solution Station 45 and 46 of an assembly line work on parts simultaneously.
Chapter 1 Design a sequential function chart Example situation Example solution At station 12, the machine drills, taps, and bolts a part. The steps occur one after the other. Sequence Step 12 inspects a process for the correct mix of chemicals. • If OK, then continue with the remaining steps. Wire • If not OK, go to the top of the SFC and purge the system. Sequence A sequence is a group of steps that execute one after the other.
Design a sequential function chart Chapter 1 • The SFC takes the first TRUE path. • The Logix Designer application lets you change the order in which the SFC checks the transitions (see chapter 2, Program a Sequential Function Chart on page 55). Simultaneous branch A simultaneous branch represents paths (steps or group of steps) that occur at the same time (an AND structure). • All paths execute. • All paths must finish before continuing with the SFC.
Chapter 1 Design a sequential function chart Wire to a previous step You can also connect a step to a previous point in your SFC.
Design a sequential function chart Add actions for each step Chapter 1 Use actions to divide a step into the different functions that the step performs, such as commanding a motor, setting the state of a valve, or placing a group of devices in a specific mode. How do you want to use the action? There are two types of actions.
Chapter 1 Design a sequential function chart To program a non-Boolean action, you have these options. If you want to Then • Execute your logic without additional routines Embed structured text. • Use structured text assignments, constructs, and instructions When the S_Complete_the_Batch step is active, the S_Open_Outlet action executes. The action sets the Outlet.ProgCommand tag equal to 1, which opens the outlet valve. • Re-use logic in multiple steps Call a subroutine.
Design a sequential function chart Chapter 1 Example When the S_Complete_the_Batch step is active, the S_Open_Outlet action executes. When the action is active, its Q bit turns on. A ladder Logic routine monitors the Q bit (S_Open_Outlet.Q ). When the Q bit is on, the JSR instruction executes and opens the outlet valve. You can reuse a Boolean action multiple times within the same SFC. SFC_ACTION structure Each action (non-Boolean and Boolean) uses a tag to provide information about the action.
Chapter 1 Design a sequential function chart If you want to Then select or set this member Data type Details Determine how many times an action has become active Count DINT This is not a count of scans of the action. • The count increments each time the action becomes active. • It increments again only after the action goes inactive and then active again. • The count resets only if you configure the SFC to restart at the initial step.
Chapter 1 Design a sequential function chart Choose a qualifier for an action Each action (non-Boolean and Boolean) uses a qualifier to determine when it starts and stops. The default qualifier is N Non-Stored. The action starts when the step is activated and stops when the step is deactivated. To change when an action starts or stops, assign a different qualifier.
Chapter 1 Design a sequential function chart Define the transition conditions The transition is the physical conditions that must occur or change in order to go to the next step. Transitions occur in these structures. 30 For this structure Make sure that Sequence A transition is between each step. Selection branch Transitions are inside the horizontal lines. Simultaneous branch Transitions are outside the horizontal lines.
Design a sequential function chart Chapter 1 Example You want to complete these steps. 1. Turn on 2 compressors. When a compressor is on, the Device1State bit is on. 2. When both compressors are on, go to the next step. Example You want to complete these steps. 1. Package the product. When the product is in the package, the package_done bit turns on. 2. Pack the product either 8 per carton or 16 per carton.
Chapter 1 Design a sequential function chart If you want to Then Enter the conditions as an expression in structured text. Use a BOOL expression on page 32 Enter the conditions as instructions in another routine. Call a subroutine on page 68 Use the same logic for multiple transitions. Use a BOOL expression The simplest way to program the transition is to enter the conditions as a BOOL expression in structured text.
Design a sequential function chart Chapter 1 Call a subroutine. Check for the required conditions. When those conditions are TRUE, turn on a BOOL tag. Use an EOT instruction to set the state of the transition equal to the value of the BOOL tag. When the BOOL tag is on (TRUE), the transition is TRUE. Transition after a specified time Each step of the SFC includes a millisecond timer that runs whenever the step is active. Use the timer to for these situations.
Chapter 1 Design a sequential function chart Description Step becomes active. X bit turns on. Timer clears and then begins to increment. DN bit turns off. The following shows the action of the low and high alarms for a step. Description AlarmEn is on. To use the low and high alarms turn this bit on. Turn the bit on via the properties dialog box or the tag for the step. Step becomes active. X bit turns on. Timer (T) begins to increment. Step becomes inactive. X bit turns off. Timer retains its value.
Design a sequential function chart Chapter 1 Description Step becomes inactive. X bit turns off. Timer retains its value. AlarmHigh stays on. (You have to manually turn it off.) Example Here is an example of the use of the Preset time of a step. The functional specification has these requirements. 1. Cook the ingredients in the tank for 20 seconds. 2. Empty the tank. Example Here is an example of the use of the high alarm of a step. The functional specification has these requirements. 1. Home 8 devices.
Chapter 1 Design a sequential function chart Programmatic reset Automatic reset Use logic to clear data Let the controller automatically clear data Each option requires you to make these decisions. • Choose a last scan option. • Based on the last scan option, develop your logic so that the last scan returns data to the correct values. Choose a last scan option On the last scan of each step, you have these options.
Design a sequential function chart Chapter 1 The following table compares the different options for handling the last scan of a step. Characteristic Execution actions During the last scan of a step, this option does Don’t scan Programmatic reset Automatic reset Only P and P0 actions execute. They execute according to their logic. All actions execute according to their logic. • P and P0 actions execute according to their logic. • All other actions execute in Postscan mode.
Chapter 1 Design a sequential function chart Use the Don’t Scan option The default option for handling the last scan of a step is Don’t scan. With this option, all data keeps its current values when the SFC leaves a step. This requires you to use additional assignments or instructions to clear any data that you want to turn off at the end of a step. Follow these steps to turn off a device at the end of a step. 1.
Design a sequential function chart Chapter 1 2. Clear the required data using any of these methods. • To your normal logic, add logic that clears the required data. Use the LS bit of the step or the Q bit of the action to condition the execution of the logic. • Use a P0 Pulse (Falling Edge) action to clear the required data. Make sure that the P0 action or actions are last in the order of actions for the step.
Chapter 1 Design a sequential function chart When the action is not on its last scan (conveyor_start.Q =1), this statement turns on conveyor_state. When conveyor_state turns on, the conveyor turns on. On the last scan of the action (conveyor_start.Q =0), this statement turns off conveyor_state. When conveyor_state turns off, the conveyor turns off. You can also use a P0 Pulse (Falling Edge) action to clear data (see Use the programmatic reset option on page 38).
Design a sequential function chart Important: Chapter 1 The postscan of an action actually occurs when the action goes from active to inactive. Depending on the qualifier of the action, the postscan could occur before or after the last scan of the step. As a general rule, the postscan executes instructions as if all conditions are FALSE. For example, the Output Energize (OTE) instruction clears its data during postscan. Follow these steps to automatically turn off (clear) devices at the end of a step.
Chapter 1 Design a sequential function chart Keep something on from step-to-step How do you want to control the device? To provide bumpless control of a device during more than one time or phase (step), do one of the following options. Option Example Use a simultaneous branch on page 42 Make a separate step that controls the device. Store and reset an action on page 43 Note the step that turns on the device and the step that turns off the device.
Design a sequential function chart Chapter 1 Example A paint operation completes these actions. 1. Transfers the product into the paint shop. 2. Paints the product using 3 separate paint guns. 3. Cleans the guns. 4. Transfers the product to the paint ovens. During the entire process, the system must control the shop fans. Store and reset an action Typically, an action turns off (stops executing) when the SFC goes to the next step.
Chapter 1 Design a sequential function chart When the SFC leaves the step that stores the action, the Logix Designer application continues to show the stored action as active. By default, a green border displays around the action. This lets you know that the SFC is executing the logic of that action. To use a stored action, follow these guidelines. • The Reset action only turns off the stored action. It does not automatically turn off the devices of the action.
Design a sequential function chart Chapter 1 In this example, a step turns on a fan and then calls another SFC. The nested SFC sequences the remaining functions of the step. The fan stays on throughout the steps of the nested SFC. Example Use a Large Step This action turns on a fan. • fan.ProgProgReq lets the SFC command the state of the fan. • fan.ProgCommand turns on the fan. This action calls another SFC. The SFC sequences the remaining functions of the step.
Chapter 1 Design a sequential function chart • The X bit of the stop element turns on. This signals that the SFC is at the stop element. • Stored actions remain active. • Execution stops for part or all of the SFC. If the stop element is at the end of a Then • Sequence The entire SFC stops • Selection branch • Path within a simultaneous branch Only that path stops while the rest of the SFC continues to execute.
Design a sequential function chart Chapter 1 Example This example shows the use of the SFC Reset (SFR) instruction to restart the SFC and clear the X bit of the stop element (see Restart (reset) the SFC on page 46). If SFC_a_stop.X = on (SFC_a is at the stop) and SFC_a_reset = on (time to reset the SFC) then for one scan (ons[ 0 ] = on): Reset SFC_a to SFC_a_Step_1 SFC_a_stop.X = 0 SFC_STOP structure Each stop uses a tag to provide information about the stop element.
Chapter 1 Design a sequential function chart Nest an SFC One method for organizing your project is to create one SFC that provides a high-level view of your process. Each step of that SFC calls another SFC that performs the detailed procedures of the step (nested SFC). This figure shows one way to nest an SFC. In this method, the last scan option of the SFC is configured for either Programmatic reset or Don’t Scan. If you configure the SFC for Automatic reset, then step 1 in is unnecessary.
Design a sequential function chart Chapter 1 Pass parameters To pass parameters to or from an SFC, place a Subroutine/Return element in the SFC. Configure when to return to the OS/JSR By default, an SFC executes a step or group of simultaneous steps and then returns to the operating system (OS) or the calling routine (JSR). You have the option of letting the SFC execute until it reaches a false transition.
Chapter 1 Design a sequential function chart Select the Execute until FALSE transition option only when either of these are true: Pause or reset an SFC • You do not have to update JSR parameters before each step. Parameters update only when the SFC returns to the JSR. • A FALSE transition occurs within the watchdog timer for the task. If the time that it takes to return to a JSR and complete the rest of the task is greater than the watchdog timer, a major fault occurs.
Design a sequential function chart Chapter 1 The following diagram shows the execution of a sequence.
Chapter 1 Design a sequential function chart The following diagram shows the execution of a simultaneous branch.
Design a sequential function chart Chapter 1 The following diagram shows the execution of a selection branch.
Chapter 1 Design a sequential function chart The following diagram shows options for execution control.
Chapter 2 Program a sequential function chart Introduction To add SFC elements, use the SFC toolbar. Add and manually connect elements 1. On the SFC toolbar, click the button for the item that you want to add. 2. Drag the element to the required location on the SFC. 3. To wire (connect) two elements together, click a pin on one of the elements and then click the pin on the other element . A green dot shows a valid connection point.
Chapter 2 Program a sequential function chart Important: Use caution when copying and pasting components between different versions of the Logix Designer application. The application only supports pasting to the same version or newer. Pasting to a prior version of the application is not supported. When pasting to a prior version, the paste action may succeed but the results may not be as intended. Add and automatically connect elements 1. Click the element to which you want to connect a new element. 2.
Program a sequential function chart Chapter 2 2. To add a path to the branch, click the first step of the path that is to the left of where you want to add the new path. Click . 3. To wire the simultaneous branch to the preceding transition, click the and then click the horizontal line of the bottom pin of the transition branch . A green dot shows a valid connection point. End a simultaneous branch 1. Select the last step of each path in the branch. To select the steps, do either of these actions.
Chapter 2 Program a sequential function chart 3. Add the transition that follows the simultaneous branch. 4. To wire the simultaneous branch to the transition, click the top pin of the and then click the horizontal line of the branch .A transition green dot shows a valid connection point. Create a selection branch Start a selection branch 1. On the SFC toolbar, click the to the correct location. button. Then drag the new branch 2.
Program a sequential function chart Chapter 2 End a selection branch 1. Select the last transition of each path in the branch. To select the transitions, do either of these actions. • Drag the pointer around the transitions that you want to select. • Click the first transition. Hold down Shift while clicking the rest of the transitions that you want to select. 2. On the SFC toolbar, click . 3. Add the step that follows the selection branch. 4.
Chapter 2 Program a sequential function chart 2. Clear the Use default priorities check box and select a transition. Use the Move buttons to raise or lower the priority of the transition. 3. When all the transitions have the correct priority, click OK. When you clear the Use default priorities check box, numbers show the priority of each transition. Connect a wire to the step 60 You may have to reposition a wire after you connect it to a step. This example shows how to go to Step_001 from Tran_003.
Program a sequential function chart Chapter 2 Click the lower pin of the transition that signals the jump. Then click the top pin of the step to which you want to go. A green dot shows a valid connection point. Typically, the resulting connection orients itself along the center of the flowchart and is hard to see. To make the jump easier to read, drag its horizontal bar above the step to which the jump goes. You may also have to reposition some of the SFC elements.
Chapter 2 Program a sequential function chart Location to which the wire goes Configure a step Assign the preset time for a step 1. Click the button of the step. 2. In the Step Properties dialog box, on the General tab, in the Preset box, enter the time for the step, in milliseconds. 3. Click OK. When the step is active for the preset time (Timer = Preset), the DN bit of the step turns on. To calculate the preset time for a step at runtime, see Use an expression to calculate a time on page 63.
Program a sequential function chart Chapter 2 Use an expression to calculate a time To calculate a time based on tags in your project, enter the time as a numeric expression. You can use an expression to calculate these values. • Preset • LimitHigh • LimitLow Follow these steps to enter a time as an expression. 1. Click the button of the step. 2. In the Step Properties dialog box, on the General tab, select the Use Expression check box. 3. Click Define and enter an expression.
Chapter 2 Program a sequential function chart Program a transition Enter a BOOL expression The simplest way to program the transition is to enter the conditions as a BOOL expression in structured text. 1. Double-click the text area of the transition. 2. Type the BOOL expression that determines when the transition is TRUE or FALSE. 3. To close the text entry window, press Ctrl+Enter. This example shows three transitions that use a BOOL expression (see Enter a BOOL expression on page 64).
Program a sequential function chart Chapter 2 Call a subroutine when programming a transition 1. In the SFC, right-click the transition and then click Set JSR. 2. In the Routine box, click the down arrow and then click the routine that you want to call. 3. Click OK. Add an action Configure an action To add an action to a step, right-click the step in which the action executes and then click Add Action. Change the qualifier of an action A qualifier determines when an action starts and stops.
Chapter 2 Program a sequential function chart 2. In the Action Properties dialog box, on the General tab, select the qualifier for the action. If you chose a timed qualifier, type the time limit or delay for the action, in milliseconds. These are the timed qualifiers. • L Time Limited • SL Stored and Time Limited • D Time Delayed • DS Delayed and Stored • SD Stored and Time Delayed 3. Click OK.
Program a sequential function chart Chapter 2 Browse for a tag Choose a function Choose an operator Create a tag 4. Enter a numeric expression that defines the preset time. Use the buttons on the right side of the dialog box to help you complete the expression. 5. Click OK. 6. To close the Action Properties dialog box, click OK. Mark an action as a BOOLean action Use a Boolean action to only set a bit when the action executes. 1. Click the button in the action. 2.
Chapter 2 Program a sequential function chart 1. Double-click the text area of the action. 2. Type the required structured text. 3. To close the text entry window, press Ctrl+Enter. Call a subroutine in an action Use a Jump to Subroutine (JSR) instruction to execute a subroutine when the action is active. 1. In the SFC, right-click the action and then click Set JSR. 2. In the Routine box, click the down arrow and then click the routine that you want to call. 3.
Program a sequential function chart Chapter 2 5. Click OK. Assign the execution order of actions Actions execute in the order in which they appear. When Step_003 is active, its actions execute in this order. 1. Action_000 2. Action_001 3. Action_002 To change the order in which an action executes, drag the action to the correct location in the sequence. A green bar shows a valid placement location. The following shows dragging Action_002 from after Action_001 to before Action_001.
Chapter 2 Program a sequential function chart Document an SFC You can document these SFC components.
Program a sequential function chart • Alarm Messages (in ALARM_ANALOG and ALARM_DIGITAL configuration) • Tasks • Property descriptions for modules in the Controller Organizer • Rung comments, SFC text boxes, and FBD text boxes Chapter 2 For more information on enabling a project to support multiple translations of project documentation, see the online help.
Chapter 2 Program a sequential function chart Add a tag description 1. Click the button of the element. 2. In the element Properties dialog box, click the Tag tab and type the description for the element. 3. Click OK. 4. Drag the description box to the correct location on the SFC. Add a text box A text box lets you add notes that clarify the function of an SFC element (step, transition, or stop. Text boxes are only stored in the offline, ACD project file.
Program a sequential function chart If you the text box to Then Stay in the same spot Stop. You are done. Move with the element to which it applies Go to step 5. Chapter 2 5. Click the pin symbol in the text box and then click the SFC element to which you want to attach the text box. A green dot shows a valid connection point. Show or hide text boxes or tag descriptions You have the option of showing or hiding both text boxes and tag descriptions.
Chapter 2 Program a sequential function chart 2. Select the Never display description in routine check box. 3. Click OK. Configure the execution of the SFC The SFC Execution tab of the controller properties lets you configure these decisions. • What to do when a transition is TRUE. • Where to start after a transition to the Run mode or recovery from a power loss. • What to do on the last scan of a step. 1. On the Online toolbar, click the controller properties button. 2.
Chapter 2 Program a sequential function chart Verify the routine As you program your routine, periodically verify your work. 1. In the top-most toolbar of the application window, click . 2. Follow these steps if any errors are listed in the Output window. a. To go to the first error or warning, press F4. b. Correct the error according to the description in the in the Output window on the Search Results tab. c. Go to step 1. 3. To close the Results window, press Alt+1.
Chapter 2 76 Program a sequential function chart • Modify indicator tags • Add, delete or modify an SBR/RET • Add, delete or modify any step or action expression Rockwell Automation Publication 1756-PM006F-EN-P - October 2014
Chapter 3 Force steps Introduction Use a force to override data that your logic either uses or produces. • Test and debug your logic. • Temporarily keep your process functioning when an input device has failed. Use forces only as a temporary measure. They are not intended to be a permanent part of your application. Precautions Make sure you understand the following before using forces. ATTENTION Forcing can cause unexpected machine motion that could injure personnel.
Chapter 3 Force steps Important: If you download a project that has forces enabled, the programming software prompts you to enable or disable forces after the download completes. When forces are in effect (enabled), a Disable or remove a force To stop the effect of a force and let your project execute as programmed, disable or remove the force. • You can disable or remove I/O and SFC forces at the same time or separately. • Removing a force on an alias tag also removes the force on the base tag.
Force steps Chapter 3 Forces tab ----------> Forces tab status Means Enabled • If the project contains any forces of this type, they are overriding your logic. • If you add a force of this type, the new force immediately takes effect Disabled Forces of this type are inactive. If the project contains any forces of this type, they are not overriding your logic. Installed At least one force of this type exists in the project. None Installed No forces of this type exist in the project.
Chapter 3 Force steps Important: The ForceStatus attribute shows only the status of I/O forces. It does not show the status of SFC forces. where: Force_Status is a DINT tag. Step through a transition or a force of a path To determine if Examine this bit For this value forces are installed 0 1 no forces are installed 0 0 forces are enabled 1 1 forces are disabled 1 0 To override a false transition one time and go from an active step to the next step, use the Step Through option.
Force steps When to use an SFC force Chapter 3 To override the logic of an SFC, you have these options. If you want to Then Override the conditions of a transition each time the SFC reaches the transition Force a transition. Prevent the execution of one or more paths of a simultaneous branch Force a simultaneous path. Force a transition To override the conditions of a transition through repeated executions of an SFC, force the transition. The force remains until you remove it or disable forces.
Chapter 3 Force steps For example, to exit this branch, the SFC must be able to complete these actions. • Execute Step_011 at least once • Get past Tran_011 and execute Step_012 at least once • Determine that Tran_012 is TRUE Force a simultaneous path To prevent the execution of a path of a simultaneous branch, force the path FALSE. When the SFC reaches the branch, it executes only the un-forced paths.
Force steps This path executes. Chapter 3 This path does not execute. If you force a path of a simultaneous branch to be FALSE, the SFC stays in the simultaneous branch as long as the force is active (installed and enabled). Add an SFC force • To leave a simultaneous branch, the last step of each path must execute at least one time and the transition below the branch must be TRUE. • Forcing a path FALSE prevents the SFC from entering a path and executing its steps.
Chapter 3 Force steps If Then Off No SFC forces currently exist. Flashing No SFC forces are active. But at least one force already exists in your project. When you enable SFC forces, all existing SFC forces will also take effect. Solid SFC forces are enabled (active). When you install (add) a force, it immediately takes effect. 2. Open the SFC routine. 3.
Index A action 71 assign qualifier 69 boolean 28 call a subroutine 72 choose between boolean and non-boolean 27 data type 29 non-boolean 27 program 27 reset 46 store 46 use expression 70 use of boolean action 28 use of structured text 71 alarm sequential function chart 35, 66 automatic reset sequential function chart 42 B E enable force 81 EOT instruction 72 expression BOOL expression 34, 68 numeric expression 67, 70 F force disable 82 enable 81 LED 82 monitor 82 remove 82 function block diagram force a
Index P periodic task application for 16 postscan sequential function chart 37 program action 27 boolean action 28 programmatic reset option 40 Q qualifier assign 69 R remove force 82 reset action 46 SFC 49 reset an SFC 51 restart sequential function chart 49 routine as transition 72 nest within sequential function chart 51 verify 79 S selection branch overview 24 sequential function chart action 27, 46, 71 automatic reset option 42 boolean action 28 call a subroutine 72 define tasks 16 don't scan optio
Index T task define 16 text box sequential function chart 76 show or hide in sequential function chart 77 transition BOOL expression 34 call a subroutine 34, 69 choose program method 33 EOT instruction 72 use of a subroutine 72 V verify routine 79 W wire sequential function chart 26 Rock well Automation Publication 1756-PM006F-E N-P - Oct ober 2014 87
Rockwell Automation support Rockwell Automation provides technical information on the web to assist you in using its products. At http://www.rockwellautomation.com/support you can find technical and application notes, sample code, and links to software service packs. You can also visit our Support Center at https://rockwellautomation.custhelp.com for software updates, support chats and forums, technical information, FAQs, and to sign up for product notification updates.
