Nematron Pointe Controller - Manual (Page 132)

Chapter 5: Developing Controller Programs Pointe Controller User Guide
130
Flow Chart Blocks
Flow charts contain distinct block types: Process, Terminator, Decision blocks, and
Subcharts.
Rectangles with the entry point at the top and the exit point at the bottom
represent Process blocks:
Each Process block contains a description of the action or actions to be taken. The
same Process block can contain multiple commands, with each command
executing sequentially.
Terminator blocks define the beginning and ending of a chart’s program flow:
All Flow Charts have a Start and an Exit or Return terminator block. Subcharts
return to the calling chart at a Return block.
TIP: A Flow Chart can have only one Start block, but may have more than one Exit
or Return block.
Diamonds, with an entry point located at the top and exit points on the right side
and at the bottom, represent Decision blocks:
Decision blocks include Condition, Repeat/Until Loop, and While Loop blocks. Any
yes/no question can be asked within these blocks. If you need to test two
conditions at the same time, you can describe both within the test block by using
the logical AND, OR, XOR, and NOT operators. For example:
START_PB = ON AND EMERGENCY = OFF
With the Repeat/Until Loop and the While Loop blocks, you can design a block
that repeats commands. The Repeat/Until Loop continues to ask the questions
contained in its block until its conditions become true. The While Loop continues
to ask the questions contained in the block until its conditions are no longer true.
Flow Charts are event-driven diagrams that do not depend on time constraints,
although you can assign a time-out to a decision block. When the timeout-
defined number of microseconds passes, the program proceeds to the Else path,
even if the block has not fulfilled all of its conditions.