Jump to Subroutine (JSR), Subroutine (SBR), and Return (RET)

This information applies to the

CompactLogix

5370,

ControlLogix

5570,

Compact GuardLogix

5370,

GuardLogix

5570,

Compact GuardLogix

5380,

CompactLogix

5380,

CompactLogix

5480,

ControlLogix

5580, and

GuardLogix

5580 controllers.

The JSR instruction invokes another routine. When that routine completes, the execution returns to the JSR instruction.

The SBR instruction receives the input parameters passed by the JSR.

The RET instruction passes return parameters back to the JSR and ends the scan of the subroutine.

Available Languages

Ladder Diagram

Function Block

Sequential Function Chart

Structured Text

JSR(RoutineName,InputCount,InputPar,ReturnPar);

SBR(InputPar);

RET(ReturnPar);

Operands

IMPORTANT: Unexpected operation may occur if:

Output tag operands are overwritten.

Members of a structure operand are overwritten.

Except when specified, structure operands are shared by multiple instructions.

WARNING:

For each parameter in an SBR or RET instruction, use the same data type (including any array dimensions) as the corresponding parameter in the JSR instruction. Using different data types may yield unexpected results.

Ladder Diagram

JSR Instruction

Operand	Data Type CompactLogix 5370, ControlLogix 5570, Compact GuardLogix 5370, and GuardLogix 5570 controllers	Data Type CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers	Format	Description
Routine Name	ROUTINE	ROUTINE	name	Subroutine to execute
Input Par	BOOL SINT INT DINT REAL structure	BOOL SINT INT DINT LINT USINT UINT UDINT ULINT REAL LREAL structure	immediate tag array tag	Data from this routine to copy to a tag in the subroutine. Input parameters are optional Enter a maximum of 40 input parameters, if needed.
Return Par	BOOL SINT INT DINT REAL structure	BOOL SINT INT DINT LINT USINT UINT UDINT ULINT REAL LREAL structure	tag array tag	Tag in this routine to copy result from subroutine. Return parameters are optional Enter a maximum of 40 return parameters, if needed

SBR Instruction

Operand	Data Type CompactLogix 5370, ControlLogix 5570, Compact GuardLogix 5370, and GuardLogix 5570 controllers	Data Type CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers	Format	Description
Input Par	BOOL SINT INT DINT REAL structure	BOOL SINT INT DINT LINT USINT UINT UDINT ULINT REAL LREAL structure	tag array tag	Tag in this routine into which to copy the corresponding input parameter (maximum 40) from the JSR instruction.

RET Instruction

Operand	Data Type CompactLogix 5370, ControlLogix 5570, Compact GuardLogix 5370, and GuardLogix 5570 controllers	Data Type CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers	Format	Description
Return Par	BOOL SINT INT DINT REAL structure	BOOL SINT INT DINT LINT USINT UINT UDINT ULINT REAL LREAL structure	immediate tag array tag	Data from this routine to copy to the corresponding return parameter (maximum 40) in the JSR instruction.

Affects Math Status Flags

Major/Minor Faults

A major fault will occur if:	Fault type	Fault code
JSR instruction has fewer input parameters than SBR instruction	4	31
JSR instruction jumps to a fault routine	4	990 or user-supplied
RET instruction has fewer return parameters than JSR instruction	4	31
Main routine contains a RET instruction	4	31

Operation

IMPORTANT:

Any routine may contain a JSR instruction but a JSR instruction cannot call (execute) the main routine.

The JSR instruction initiates the execution of the specified routine, which is referred to as a subroutine:

The subroutine executes each time it is scanned.

After the subroutine executes, logic execution returns to the routine that contains the JSR instruction and continues with the instruction following the JSR.

To program a jump to a subroutine, follow these guidelines.

JSR

To copy data to a tag in the subroutine enter an input parameter.

To copy a result of the subroutine to a tag in this routine, enter a return parameter.

Enter up to 40 inputs and enter up to 40 return parameters as needed.

SBR

If the JSR instruction has an input parameter enter an SBR instruction.

Place SBR instruction as the first instruction in the routine.

For each input Parameter in the JSR Instruction, enter the tag into which you want to copy the data.

RET

If the JSR instruction has a return parameter, enter an RET instruction.

Place the RET instruction as the last instruction in the routine.

For each return parameter in the JSR instruction, enter a return parameter to send to the JSR instruction.

In a ladder routine, place additional RET instructions to exit the subroutine based on different input conditions, if required (Function block routines only permit one RET instruction).

Invoke up to 25 nested subroutines, with a maximum of 40 parameters passed into a subroutine, and a maximum of 40 parameters returned from a subroutine.

TIP:

Select the Edit > Edit Ladder Element
menu to add and remove variable operands. For the JSR and SBR instructions, add Input Parameter. For JSR and RET instructions, add Output Parameter. For all three instructions, remove Instruction Parameter.

Execution

Ladder Diagram

Condition/State	Action Taken
Prescan	The rung is set to false. The controller executes all subroutines. To ensure that all rungs in the subroutine are prescanned, the controller ignores RET instructions (that is, RET instructions do not exit the subroutine). Input and return parameters are not passed. If the same subroutine is invoked multiple times, it will only be prescanned once.
Rung-condition-in is false (to the JSR instruction)	N/A
Rung-condition-in is true	Parameters are passed and the subroutine is executed.
Postscan	Same action as Prescan

Function Block

Condition/State	Action Taken
Prescan	See Prescan in the Ladder Diagram table.
EnableIn is false	N/A
EnableIn is true	Parameters are passed and the subroutine is executed
Instruction first run	N/A
Instruction first scan	N/A
Postscan	See Postscan in the Ladder Diagram table.

Structured Text

Condition/State	Action Taken
Prescan	See Prescan in the Ladder Diagram table.
Normal Execution	Parameters are passed and the subroutine is executed.
Postscan	See Postscan in the Ladder Diagram table.

Examples

Example 1

Ladder Diagram

Structured Text

Routine	Program
Main routine	JSR(routine_1,2,value_1,value_2,float_value_1);
Subroutine	SBR(value_a,value_b); <statements>; RET(float_a);

Example 2

Ladder Diagram

Main routine

subroutine_1

Example 3

Function Block

Program Control Instructions

Add Input Parameter command

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