Introduction.

Workshop PG5
Project management
6.5 General structure of an SB
Initial STEP
Transition
STEP
Sequential blocks are built out of different elements which are called:
Initial Step
Step
Transition
SB’s start with an Initial STEP. When you call the SB for the very first time, then the
SB will execute the program code inside the Initial Step.
6.6 Basic rule: Alternate STEPS & Transitions
Sequential blocks have a strict syntax.
A sequential block always starts with an “Initial Step”
Thereafter transitions and steps must alternate all the time.
You must never have two Steps or two Transitions in a row.
Right
Wrong
In contrast to other PLC's, SAIA PCD’s have implemented the SequentialBlockengine
in the firmware which makes the sequential blocks extremely fast.
PG5-06-E.doc © Saia-Burgess Controls Ltd. Page 6-8