RSLogix JMP & LBL Instructions – Jump and Label Guide
Published on Aug 18, 2025 | Category: Program ContolShare this Page:
Jump (JMP) and Label (LBL) are key program control instructions in RSLogix 5000.
They help manage the flow of large and complex PLC programs efficiently.
The JMP instruction allows the program to skip specific sections of ladder logic and jump to a corresponding LBL instruction. This helps control which parts of the program execute under different conditions.The LBL instruction serves as a target or marker for JMP. Together, JMP and LBL make ladder logic programs more organized, modular, and easier to maintain.
What is a Label (LBL) Instruction in RSLogix 5000?
The Label (LBL) instruction is used in RSLogix 5000 to mark a specific location or point in a ladder logic program. It acts as a target for the Jump (JMP) instruction, allowing the program to skip sections of ladder logic and continue execution from the labeled point. LBL itself does not perform any action; it only serves as a marker for program control flow.
What is a Jump (JMP) Instruction in RSLogix 5000?
The Jump (JMP) instruction in RSLogix 5000 is used to skip a section of ladder logic and continue program execution from a corresponding Label (LBL) instruction. It allows you to control the flow of the program, bypassing rungs that do not need to execute under certain conditions. JMP is commonly used in large or complex programs to make the ladder logic more organized and efficient.
Where JMP and LBL Instructions Are Used in RSLogix 5000
The JMP and LBL instructions are mainly used in large or complex PLC programs where controlling the flow of execution is important. They help skip unnecessary rungs and jump to specific sections of ladder logic, making the program more efficient.
Typical applications include:
- Bypassing sections of code that do not need to run under certain conditions.
- Organizing programs into modular sections for easier troubleshooting and maintenance.
- Implementing conditional logic where only specific parts of the program should execute based on process requirements.
- Improving readability and reducing program scanning time in large ladder logic projects.
Using JMP and LBL together ensures that complex sequences can be managed effectively, allowing programmers to create flexible and maintainable control systems.
Practical Example of JMP and LBL Instructions
This ladder logic demonstrates the use of JMP (Jump) and LBL (Label) instructions in RSLogix 5000. These instructions are used to control the flow of the program by skipping or jumping to a specific point in the logic.
Explanation:
- Rung 1: Checks the Safety_Switch. If it is ON, the program executes the JMP instruction to jump to LBL1. This effectively skips the conveyor start logic if the safety condition is active.
- Rung 2: Controls the conveyor operation:
- Conveyor_Start: Starts the conveyor when pressed.
- Conveyor_Stop: Stops the conveyor when pressed.
- Safety_Switch: Acts as an interlock to prevent the conveyor from running if safety is not OK.
- Conveyor_Run: Output that keeps the conveyor running using a seal-in (latching) circuit.
- Rung 3: LBL1 marks the point in the program where the jump lands.
- If the program jumps to LBL1, the conveyor logic in Rung 2 is skipped.
- Warning_Light: Output activated to indicate a safety condition.
Summary: The JMP instruction is used to skip over the conveyor start/stop logic if the safety switch is triggered. The LBL instruction marks the point to jump to, ensuring safety interlocks are prioritized and the warning light is activated.
RSLogix 5000 JMP and LBL Example with Counter & Timer
This ladder logic program demonstrates a batch process using a conveyor motor, a part counter, and a delay timer. The logic utilizes JMP and LBL instructions to keep the program organized.
Rung 1 – Start and Jump to Motor Control
When the Start push button is pressed, the JMP instruction jumps directly to the RunMotor label. This avoids unnecessary intermediate rungs and keeps the logic modular.
Rung 2 – RunMotor Label and Motor Control
The RunMotor label marks the motor control section. The motor output is energized if:
- The Start button is pressed, or
- The Motor is already running (seal-in logic),
while ensuring that the Stop button or a Safety_Switch disables the motor immediately when activated.
Rung 3 – Counter Increment
The CTU counter1 increments each time a part passes the part_counter_sensor while the motor is running. The counter preset is set to 10.
Rung 4 – Move Counter Value to PartCounter Tag
The MOV instruction moves the accumulated value of counter1 to the PartCounter tag for comparison and display purposes.
Rung 5 – Check if Batch is Complete
When PartCounter reaches 10, the JMP instruction jumps to the DelaySection label for a post-batch delay.
Rung 6 – Delay Section Label
The DelaySection label begins the delay timer sequence. The TON DelayTimer runs for a preset value (1000 ms in this example). The reset_counter bit triggers the timer.
Rung 7 – Reset Counter After Delay
Once the timer is done (DelayTimer.DN), the RES instruction resets counter1, preparing the system for the next batch.
Summary of Flow
- Press Start → jump to RunMotor section.
- Motor starts and counts parts via the CTU counter1.
- Move the accumulated counter value to PartCounter.
- When PartCounter ≥ 10 → jump to DelaySection.
- Run TON DelayTimer for a specified delay.
- After timer completion → reset counter1 and prepare for the next batch.
Advantages of JMP and LBL in This Program
- Jump instructions allow skipping intermediate rungs and keep logic modular.
- Labels provide reference points to organize different sections of the process.
- Reduces duplicate logic and improves readability.
- Ideal for batch processes, counters, and timers.