Siemens SIMATIC ET 200SP System Manual page 126

Basics of program execution
7.3 Asynchronous instructions
Assignment of call to job of the instruction
To execute an instruction over multiple calls, the CPU must be able to uniquely assign a
subsequent call to a running job of the instruction.
To assign a call to a job, the CPU uses one of the following two mechanisms, depending on
the type of the instruction:
● The instance of the instruction (with type "SFB")
● The input parameters of the instruction identifying the job. These input parameters must
match in each call during processing of the asynchronous instruction.
Example: A "Create_DB" instruction job is identified by the input parameters LOW_LIMIT,
UP_LIMIT, COUNT, ATTRIB and SRCBLK.
The following table shows which instruction you can identify with which input parameters.
126
Instruction
DPSYC_FR
D_ACT_DP
DPNRM_DG
WR_DPARM
WR_REC
RD_REC
CREATE_DB
READ_DBL
WRIT_DBL
RD_DPARA
DP_TOPOL
Job 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
System Manual, 12/2015, A5E03576849-AF
Distributed I/O system