User guide

P/N: 021-00154, Rev. A.6 - updated for V4.7 Tools Page | 57
input/output status variables and then check for a non-zero sum that indicates an error condition was detected.
Given an error then examine each of the status variables to determine the problem and corrective action.
4.2 Logic Sequences
The logi
c sequence window uses bubbles (the circles) and transitions (the lines connecting the circles) to create
a logical program flow for part of the user application. Bubbles are containers for the program code while
transitions are specify bubble transition conditional logic. Each
Bubble represents a state in which the program will repeat the
same set of programmed logic until a transition logic expression is
evaluated to be true. When a transition is true like a digital switch
being closed, the program will change states to the bubble pointed
to by the transition line. Any bubble can have multiple transition
conditions pointing to different bubbles.
Also note that each logic sequence has one starting point bubble
noted by the (S) above the bubble. This is the bubble that will be
executed after power up of the controller when the logic sequence
is first executed. The starting point bubble has to be specified but
it can be changed to any bubble in the logic sequence.
Adding and Editing Bubbles
To add a bubble to a logic sequence, click the right
mouse button and select Add Bubble. To relocate a
bubble click and hold the left mouse button on top of the
bubble and move the mouse to relocate the bubble. The
transitions if any will follow the bubble. Releasing the
mouse button completes the bubble move.
To edit bubble code, double click the left mouse button
on the bubble. This displays a window with four text entry
fields and 1 check box. The Caption field identifies the
bubble in the logic sequence window and is merely a
comment. This value is also used in the Transition
Display for quick reference to the transition logic flow on
the bubble screen. The Description field will be displayed
as a comment in the logic sequence window above the bubble icon if the visible check box is checked. Use the
Entry Code box for program code that is executed when the bubble is transitioned to from another bubble. Use
the Repeat Code box for the program code that will be executed each time the DVC processor visits the bubble
before a transition to another bubble is taken. When a bubble is transitioned to or the Start bubble is executed
the Entry Code and Repeat Code are both executed. After that only the Repeat Code is executed until a
transition condition is true.
Adding and Editing Bubble Transitions
To add a bubble transition, click the right mouse button on a
bubble and select Add Bubble Transition. Next, click on the
Bubble to which you want the transition to point. Now double
click on the transition line to bring up a window with three text
fields and three check boxes. The box titled "Description" is for
placing comments about the transition. The next two fields are for the transition logic expression. A transition
logic expression is of the same form as that used in the If (…) conditional execution expression without the “if (“
and closing “)”. Conditions can be combined using the “and” and “or” logic operators. The visible check boxes