Link Type: Conditional Jump

Note:
A Link Type specifies the condition that makes the RMC jump to and execute the next step in a User Program.

The Conditional Jump link type can have one or more conditions. The conditions are evaluated in order. For the first condition that evaluates to True, the program jumps to the destination specified in its Jump On True box. If all conditions evaluate to False, then the program jumps to the destination specified in the Jump On False box.

The Jump destinations can contain a step number, a step label, ”Wait”, ”Next”, or "Repeat":

Next: The program will jump to the next step in the sequence.
Wait: The program will stop evaluating the conditions, and re-evaluate the conditions the next control loop. For Conditional Jumps with multiple link conditions, ”Wait” must only be used for the Jump On True/False boxes for the last condition, and only in one of the boxes.
Repeat: The program will repeat the entire step, which means it will issue all the commands in the step.

When the user program jumps to a step, that step is executed in the next loop time of the RMC.

Boxes

The Conditional Link Type has the following parts:

	Description
Link Condition	The Link Condition specifies the expression that is evaluated. It must be a logical expression that evaluates to True or False.
Jump On True	Specifies the step to jump to if the Link Condition is True. It must be a valid step number, step label, "Wait", "Next", or "Repeat". For Conditional Jumps with multiple link conditions, ”Wait” must only be used for the Jump On True/False boxes for the last condition, and only in one of the boxes.
Jump On False	Specifies the step to jump to if the Link Condition is False. It must be a valid step number, step label, "Wait", "Next", or "Repeat". For Conditional Jumps with multiple link conditions, ”Wait” must only be used for the Jump On True/False boxes for the last condition, and only in one of the boxes.

To select the Conditional Jump Link Type:

Open or create a User Program.
Go to the step where you want the Conditional Jump Link Type.
Double-click the Link Type box.
Click Cnd Jump.

Editing the Link Condition

Each Link Condition box in the Conditional Jump Link Type must contain a single logical (comparison) expression. To begin creating the expression, double-click the Link Condition box. The Expression Editor will open to assist you in entering an expression. See the Expressions Overview topic for details on creating expressions.

Adding and Deleting Link Conditions

To add a Link Condition, right-click the Link Condition box and choose Add Before or Add After, or click the Add Link Condition After button on the Step Editor toolbar.
To delete a Link Condition, right-click the Link Condition box and press Delete, or click the Delete Link Condition button.
To move a Link Condition, select the Link Condition box and click the Move Link Condition Up or Move Link Condition Down buttons.

Example

See the Example: Time-out topic for an example of using the Conditional Jump.

Timing Considerations

Beginning with the loop time after the step containing the Conditional Jump link type is executed, the RMC will monitor the Conditional Jump link condition. In the same loop time that the condition indicates a jump should be made, the program will jump to the specified step and execute it. Therefore, the specified step can be executed no sooner than the next loop time after the first step was executed, and the state of the condition in the same loop time that the first step is executed is not considered.

Example 1

Consider a program where Step 0 issues a Move Absolute command and has a Conditional Jump link type with a link condition that waits for a discrete input to be on. The Jump on True contains step 1 and Jump on False contains step 2. In the loop time that step 0 is executed (the Move Absolute command is issued), the link condition is not evaluated. The next loop time, the program will evaluate the link condition. In this case, either step 1 or step 2 will be executed. If the time is 1 millisecond, and step 0 was executed at time 0 (zero), then step 1 or step 2 will be executed at time 0.001 seconds.

Example 2

Consider a program where Step 0 issues a Move Absolute command and has a Conditional Jump link type with a link condition that waits for a discrete input to be on. The Jump on True contains step 1 and Jump on False contains "Wait". In the loop time that step 0 is executed (the Move Absolute command is issued), the link condition is not evaluated. The next loop time, the program will evaluate the link condition. If the condition is true (the discrete in put is on), the program will jump to the specified step and execute it in that same loop time. If the condition is false, (the discrete in put is on), the program will wait. This will repeat until the condition is true, at which point the program will jump to the specified step and execute that step in the same loop time in which the condition became true.