Technical data

Table Of Contents
Copy and Block Functions
System Software for S7-300/400 System and Standard Functions - Volume 1/2
A5E00709327-01
3-19
3.10 Reading from a Data Block In Load Memory with
SFC 83 "READ_DBL"
Description
Use SFC 83 "READ_DBL" (read data block in load memory) to copy a DB or an
area from a DB in load memory (Micro Memory Card) to the data area of a target
DB. The target DB must be relevant for execution; that is, it must not be created
with the attribute UNLINKED. The content of the load memory is not changed
during the copy process.
To ensure consistency, you must not change the target area while the SFC83 is
being processed (i.e. as long as the BUSY parameter has the value TRUE).
The following restrictions apply to the parameters SRCBLK (source block) and
DSTBLK (destination block):
For an ANY pointer of the type BOOLEAN the length must be divisible by 8.
For an ANY pointer of the type BOOLEAN the length must be divisible by 1.
If required, you can determine the length of the source area with SFC 24
"TEST_DB".
Note
The SFC 83 is processed asynchronously. Therefore, it is not suitable for frequent
(or cyclical) reading of variables from load memory.
Note
Once started, a job is always completed. If the maximum number of simultaneously
active SFC 83 is reached and you call SFC 83 once again at this time in a priority
class having higher priority, error code W#16#80C3 will be returned. As such, it
does not make sense to restart the high-priority job right away.