Siemens CPU 948 User Manual

6.17 OB 181: Test Data Blocks (DB/DX)
With the special function organization block OB 181, you can test
data blocks as follows:
•• whether or not a particular DB or DX data block exists,
•• the address at which the first data word of the data block is stored,
•• how many data words the data block contains.
Using OB 181 The function "test DB/DX" is useful before the operations TNB/TNW,
G DB/GX DX and before calling special function organization blocks
OB 182, OB 254 and OB 255.
Before transferring data words, for example, you can call OB 181 to
check that the destination data block is valid and long enough for the
transfer.
Function OB 181 checks whether a specified data block exists and returns the
characteristic parameters of a data block.
Parameters ACCU-1-L
a)
ACCU-1-LL
Block number,
Permitted values: 1 to 255
b)
ACCU-1-LH
Block ID,
Permitted values: 1 = DB
2 = DX
OB 181: Test Data Blocks (DB/DX)
CPU 948 Programming Guide
C79000-G8576-C848-04
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Siemens CPU 948 Specifications

General

Brand	Siemens
Model	CPU 948
Category	Controller
Language	English