Alternative Branch - Siemens SIMATIC S7-GRAPH Manual

6.7

Alternative Branch

An alternative branch consists of more than one parallel path (a maximum of 125).
Each path in an alternative branch begins with a transition. Only the branch path
whose transition switches first is executed. An alternative branch therefore
corresponds to an OR operation in which only one path can be active.
Each path in an alternative branch ends with a transition and can be closed by a
branch stop or a jump.
T5
Tz
S1
T1
S2
T2
S3
T3
S4
T4
S5
T5
Jump
Priorities in Alternative Branches
If more than one transition is satisfied at the beginning of various paths, the priority
is as follows:
The transition furthest to the left has priority 1, in other words the transition located
immediately below the previous step.
The priority of all other paths of the alternative branch is decided by the transition
numbers. In this case, the transition with the lowest number has the highest
priority.
S7-GRAPH for S7-300/400 Programming Sequential Control Systems
C79000-G7076-C526-01
1 2 3
T6 T7
Sm
Sx
Tm
Tx
Tx+1
Sn
Sy
Tn
Sz
Ty
Tz
Jump
Programming the Structure of the Sequencer
:
Alternative sub-branch 1
:
Alternative sub-branch 2
:
Alternative sub-branch 3 with a
further alternative branch
6-7