Siemens SIMATIC S7-1500 System Manual page 123

Assignment of c all to job of the instruction
To execute an instruction over multiple calls, the CPU must be able to uniquely relate a
subsequent call to a running job of the instruction.
To relate a call to a job, the CPU uses one of the following two mechanisms, depending on
the type of the instruction:
● Using the instance data block of the instruction (for "SFB" type)
● Using job-identifying input parameters of the instruction. These input parameters must
match in each call during processing of the asynchronous instruction.
Example: A job of the "Create_DB" instruction is identified by input parameters
LOW_LIMIT, UP_LIMIT, COUNT, ATTRIB and SRCBLK.
The following table shows which input parameters you use to identify which instruction.
Automation system
System Manual, 09/2016, A5E03461182-AD
In struction
DPSYC_FR
D_ACT_DP
DPNRM_DG
WR_DPARM
WR_REC
RD_REC
CREATE_DB
READ_DBL
WRIT_DBL
RD_DPARA
DP_TOPOL
Basics of program execution
7.3 Asynchronous instructions
Jo b is identified by
LADDR, GROUP, MODE
LADDR
LADDR
LADDR, RECNUM
LADDR, RECNUM
LADDR, RECNUM
LOW_LIMIT, UP_LIMIT, COUNT, ATTRIB,
SRCBLK
SRCBLK, DSTBLK
SRCBLK, DSTBLK
LADDR, RECNUM
DP_ID
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