Iec 61131-3 Second edition 2003-01 Programmable controllers – Part 3: Programming languages

implementation-dependent
parameters.
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61131-3 
 IEC:2003(E)
– 101 –
Table 46 - Sequence evolution
No.
Example
Rule
1
|
+----+
| S3 |
+----+
|
+ c
|
+----+
| S4 |
+----+
|
Single sequence
:
The alternation step-transition is repeated in
series.
Example:
An evolution from step S3 to step S4 shall take
place if and only if step S3 is in the active state
and the transition condition c is true.
2a
|
+----+
| S5 |
+----+
|
+-----*----+--...
| |
+ e + f
| |
+----+ +----+
| S6 | | S8 |
+----+ +----+
| |
Divergence of sequence selection:
A selection between several sequences is
represented by as many transition symbols, under
the horizontal line, as there are different possible
evolutions. The asterisk denotes left-to-right
priority of transition evaluations.
Example:
An evolution shall take place from S5 to S6 only if
S5 is active and the transition condition e is true,
or from S5 to S8 only if S5 is active and f is true
and e is false.
2b
|
+----+
| S5 |
+----+
|
+-----*-----+--...
|2 |1
+ e + f
| |
+----+ +----+
| S6 | | S8 |
+----+ +----+
| |
Divergence of sequence selection:
The asterisk, followed by numbered branches,
indicates a user-defined priority of transition
evaluation, with the lowest-numbered branch
having the highest priority.
Example:
An evolution shall take place from S5 to S8 only if
S5 is active and the transition condition f is true,
or from S5 to S6 only if S5 is active, and e is true,
and f is false.
2c
|
+----+
| S5 |
+----+
|
+------+----+--...
| |
+e +NOT e & f
| |
+----+ +----+
| S6 | | S8 |
+----+ +----+
| |