Siemens SIMATIC PCS 7 Function Manual page 23

The block monitors the 128 input structures for valid write requests. A write request is valid if
it fulfills the following conditions:
● "REC_REQ" = 1
● "MODE" <> 0
● "REQ_ID" <> 0
● "ARCH_NA" <>' '
● Either "COLUMN" <> 0 and "NO_COL" <> 0 or "NO_COL" = 0
Each valid request is allocated a priority in the order of its occurrence. Priority is allocated as
consecutive numbers from 1 to 128; 1 is the highest priority and 128 the lowest.
If no write jobs are active and there is at least one valid request pending, the request data of
the input structure with the highest priority are entered in the AS-OS coordination interface
and the data to be sent, including the request data, are copied to the send mailbox (raw data
cell). The transfer of raw data to the OS is triggered by activating the send job at the "BSEND"
block (REQ = 1).
The feedback that the send job has been executed without errors by the "BSEND" block (DONE
= 1) activates the trigger for the OS script.
Once the write job is completed on the OS, the OS enters the request data in the AS-OS
coordination interface for confirmation (this overwrites the old request data there) and sets the
"REQ_FIN" bit to "1". "REQ_FIN" = 1 compares these request data in the AS with the original
request data. If and only if they are identical, are they copied to the output structure, where
the "QWR_OK" is set. The data remain in the output structure until the write request at the
"REC_REQ" is canceled by the requesting block. This ends the write job and a new write job
can then be executed.
A write job is aborted if the requesting block cancels the "REC_REQ" request during the job.
The maximum size of the raw data cell is 16304 bytes:
ID
REQ_ID
MODE
ARCH_NA
ARCH_NO
REC_ID
NO_REC
COLUMN
NO_COL
GEN_AS
PARA_1
PARA_2
PARA_3
PARA_4
PARA_5
PARA_6
Advanced Process Functions (APF)
Function Manual, 07/2016, A5E38719883-AA
Field
INT
INT
WORD
STRING 16
DINT
DINT
DINT
DINT
DINT
DWORD
DINT
DINT
DINT
REAL
REAL
REAL
Format
2
2
2
18
4
4
4
4
4
4
4
4
4
4
4
4
Communication
2.2 FB_UA_WM
Bytes Address
0
2
4
6
24
28
32
36
40
44
48
52
56
60
64
68
23