Technical data

Table Of Contents
S7 Communication
System Software for S7-300/400 System and Standard Functions - Volume 2/2
21-22
A5E00739858-01
Data Consistency
The data are received consistently if you remember the following point:
Evaluate the last used receive areas (RD_1) completely before you call the
block again with the value 1 at control input EN_R).
Special Case for Receiving Data (S7-400 only)
If a receiving CPU with a BRCV block ready to accept data (that is, a call with
EN_R = 1 has already been made) goes into STOP mode before the
corresponding send block has sent the first data segment for the job, the following
will occur:
The data in the first job after the receiving CPU has gone into STOP mode are
fully entered in the receive area.
The partner SFB "BSEND" receives a positive acknowledgement.
Any additional BSEND jobs can no longer be accepted by a receiving CPU in
STOP mode.
As long as the CPU remains in STOP mode, both NDR and LEN have the value
0.
To prevent information about the received data from being lost, you must perform a
hot restart of the receiving CPU and call SFB 13 "BRCV" with EN_R = 1.