Siemens S7 Benutzerhandbuch
SEND/RECEIVE Interface in the User Program
74
SIMATIC NET NCM S7 for Industrial Ethernet
C79000-G8976-C129–06
3.1
How the SEND/RECEIVE Interface Works on the CPU
Functions (FCs)
The following functions (FCs) are available for handling communication on
connections:
connections:
S
AG_SEND/AG_LSEND
This block takes the user data from the specified user data area and transfers it
to the Ethernet CP.
This block takes the user data from the specified user data area and transfers it
to the Ethernet CP.
S
AG_RECV/AG_LRECV
This block transfers received user data to the user data area specified in the
call.
This block transfers received user data to the user data area specified in the
call.
The diagram below illustrates the situation. Using the FCs AG_SEND/AG_LSEND
and AG_RECV/AG_LRECV, the user program instructs the Ethernet CP to send or
receive data on the configured connection.
and AG_RECV/AG_LRECV, the user program instructs the Ethernet CP to send or
receive data on the configured connection.
Communication
connection
connection
Ethernet CP
CPU
STEP 7
user program
user program
User data
buffer
buffer
CP
database
database
Ethernet station SIMATIC S7
receive
send
User data
areas
areas
AG_RECV
AG_SEND
Figure 3-1
Interaction of the CPU and Ethernet CP on Connections
Amounts of Data
The Ethernet CP can transfer the amounts of data shown in the table below per job
on one connection:
on one connection:
Table 3-1
ISO Transport
ISO-on-TCP
TCP
UDP
Sending
8192 bytes
8192 bytes
8192 bytes
2048 bytes
Receiving
8192 bytes
8192 bytes
8192 bytes
2048 bytes