Blocks And Their Functions - Siemens SIMATIC S5-95F Manual

S5-95F
9

Blocks and Their Functions

The STEP 5 programming language offers you various blocks, such as organization blocks (OBs),
program blocks (PBs), function blocks (FBs) and data blocks (DBs). Sequence blocks (SBs) are
available for programming of sequencers.
The following chapter describes:
• the meaning of the organization blocks
• the blocks integrated in the S5-95F
9.1 Organization Blocks
Table 9.1 lists the organization blocks of the S5-95F.
OB No.
OB1 Cyclic program processing
OB2 Interrupt-driven program processing (OB2 interrupts)
OB3 Interrupt-driven program processing (OB3 interrupts)
OB13 Time-controlled program processing
OB21 Restart procedure after manual POWER ON (STOP RUN)
OB22 Restart procedure after power recovery
OB31 Scan time triggering of hardware watchdog
OB34 Procedure after battery failure
OB37 Error handling
OB251 PID algorithm
Table 9-2. Restrictions of the STEP 5 Commands in Various Blocks
Command
Boolean logic operations
Set/reset operations
Load and transfer operations
Timer, counter, comparison,
block call operations
Supplementary operations
System operations
X = permissible in the OB and in PBs, SBs and FBs called there
0 = permissible only in called-up FBs
- = not permissible
1) Impractical with PII
2) Direct access to external I/Os not permissible
EWA 4NEB 812 6210-02
Table 9-1. Overview of Organization Blocks
OB 1
OB 34
OB 37
X
X
2)
X
X
0
0
Function
OB 2 OB 3
only with
IB 32, 33, X
56, 60
only
RQ 32.x X
RI 60.x
2)
- X
only BE X
- 0
- 0
Blocks and Their Functions
OB 21
OB 13
OB 22
1)
X X
1)
X X
1)2)
X X
X X
0 0
0 0
9-1