Siemens SIMATIC NET S7-300 Manual page 34

1 Communication via Ethernet CPs in S7 Stations
1.6 FETCH/WRITE Services (Server)
Application
In addition to the SEND/RECEIVE interface, the FETCH/WRITE functionality
provides further services for S5-compatible communication on configured transport
connections.
The FETCH/WRITE interface is used primarily to attach SIMATIC S7 to SIMATIC
S5 and to other non-S7 stations (for example PCs).
S FETCH
The partner on the connection (SIMATIC S5 or non-S7 station) can read
system data on the SIMATIC S7 PLC.
S WRITE
The partner on the connection (SIMATIC S5 or non-S7 station) can write
system data on the SIMATIC S7 PLC.
From the point of view of the SIMATIC S7 PLC, this is a passive communication
function that simply needs to be configured, the communications partner initiates
the connection establishment.
For further information, refer to the system documentation of the SIMATIC S5 PLC
or the non-S7 station you are using.
Connection Types
To access a station with FETCH or WRITE functions, a FETCH passive or WRITE
passive connection must be configured. The following types are possible:
S ISO Transport
S ISO-on-TCP
S TCP
Coordinating Access Using the User Program
To coordinate access, you can use the FCs AG_LOCK and AG_UNLOCK.
With these FCs, you can coordinate access to system data areas by enabling and
disabling the connections so that no inconsistent data is created and transferred.
SIMATIC S5
On the SIMATIC S5 station, the FETCH/WRITE services are configured and
started by READ ACTIVE/PASSIVE and WRITE ACTIVE/PASSIVE.
A -34
S7-CPs for Industrial Ethernet Configuring and Commissioning
Release 01/2007
C79000-G8976-C182-07