S7-GRAPH for S7-300/400 Programming Sequential Control Systems
C79000-G7076-C526-01
15-1
15
Instance DB
Each S7-Graph FB is assigned an instance data block that can be understood as
representing the memory of the FB. It contains the data belonging to the
sequencer, in other words all the data and parameters required to execute the FB.
•
all the FB parameters of the selected FB parameter set
•
step-transition description (for example current or last activation time of a step
with and without disturbance times; indicator whether or not a step is active).
The data are entered automatically.
15.1
Settings for the Instance DB
Include Instance DB
To create the instance DB automatically after compiling an error-free FB, click the
option "Include Instance DB" in the "General" tab page (menu command Options >
Application Settings). If you select this option, whenever you compile or
download the block, S7-Graph checks whether it is necessary to create or update
the instance DB and takes whatever action is necessary.
Interface Description
In the "Save/Compile" tab, there are two possible settings for the interface
description of the instance DB:
•
Structure
Arrays
If you select “Structure Arrays", detailed information about the sequencer
(transitions, steps, sequencer statuses, etc.) is entered sequentially in the
instance DB. The instance DB is evaluated by accessing the corresponding
data arrays.
•
Individual Structures
If you select "Individual structures", a separate structure with detailed
information is created for each step and each transition of the sequencer. The
structure names are the same as the names of the steps and transitions in the
sequencer. With this option, the instance DB can be evaluated both using direct
access to the data arrays as well as using the step and transition names. The
structures created increase the memory requirements of the instance DB in the
work memory but do not affect the speed of execution.