Siemens SIMATIC NET S7-300 - Page 93

4 SEND/RECEIVE Interface in the User Program
A-93
S7-CPs for Industrial Ethernet Configuring and Commissioning
Release 01/2007
C79000-G8976-C182-07
Calling FCs in the CPU Program
One possible sequence for FCs in conjunction with the organization and program
blocks in the CPU cycle is illustrated in the following diagram.
ÇÇÇÇÇÇÇÇ
ÇÇÇÇÇÇÇÇ
ÍÍÍÍÍÍÍÍ
ÍÍÍÍÍÍÍÍ
AG_RECV
ÍÍÍÍÍÍÍÍÍ
ÍÍÍÍÍÍÍÍÍ
AG_SEND
AG_SEND
Read in the received
data of the
connection
Transfer send data
for the connection
Write PIQ
OB
ÇÇÇÇÇÇÇÇÇ
ÇÇÇÇÇÇÇÇÇ
ÇÇÇÇÇÇÇÇÇ
Legend:
Sequence of the CPU cycle
AG_RECV
AG_RECV
Communication
connection
ÇÇÇÇÇÇÇ
ÇÇÇÇÇÇÇ
ÇÇÇÇÇÇÇ
ÇÇÇÇÇÇÇ
ÍÍÍÍÍÍÍ
ÍÍÍÍÍÍÍ
ÍÍÍÍÍÍÍ
ÍÍÍÍÍÍÍ
ÍÍÍÍÍÍÍ
AG_SEND
User program
The different shading shows which
connections and FC blocks belong
together.
ÇÇ
ÇÇ
ÍÍ
ÍÍ
Read PII
Communication
connection
Communication
connection
Figure 4-2 Typical Sequence of Function Calls in the CPU Cycle
The following points are illustrated by the diagram:
 The user program consisting of any number of blocks (OBs, FBs or FCs -> see
also /6/ accesses several connections (Figure 4-2 illustrates three connections).