Block Types - Siemens SIMATIC S5-90U System Manual

Introduction to STEP 5
7.3

Block Types

The following Table lists the most important characteristics of the individual block types.
Block
types
Characteristics
Number in
S5-90U OB1, 3, 21, 22
Number in
S5-95U OB1, 3, 13, 21,
22, 31, 34, 251
Length (max.) in
S5-90U
Length (max.) in
S5-95U
Operations set
(contents)
Representation
methods
Block header
length
1
Data blocks are already integrated into the operating system (see Chapter 9).
2
Data blocks DB0 and DB1 are reserved.
3
SB2 is already integrated in the operating system (see Chapter 9).
7-6
Table 7-2. Comparison of Block Types
OB PB
4 64
PB0 to PB63
8 256
PB0 to PB255
4 KB 4 KB
8 KB 8 KB
Basic Basic
operations operations
STL, CSF, STL, CSF,
LAD LAD
5 words 5 words
SB FB
64
FB0 to FB63
3 1
256 256
SB0 to SB255 FB0 to FB255
4 KB
8 KB 8 KB
Basic Basic,
operations supplementary,
system
operations
STL, CSF,
STL
LAD
5 words
5 words
+parameters
EWA 4NEB 812 6115-02b
S5-90U/S5-95U
DB
2
62
DB2 to DB63
2
254
DB2 to DB255
256
data words
256
data words
Bit pattern
Numbers
texts
5 words