Simatic Fetch/Write

Fetch/Write (ISO-on-TCP RFC 1006)

The protocol Simatic Fetch/Write enables the connection of S7 automation devices with any communication partner. It provides direct access to the S7 user memory without changes in the user application itself, if applicable.

Only a communication unit (CP) for Ethernet connection or alternatively an onboard Ethernet interface that supports ISOonTCP (RFC1006) as well as the protocol Simatic Fetch/Write must be available.

An onboard Ethernet interface requires the development of special function modules for the communication in addition to the S7 user program. This is not necessary with an external communication unit (CP).

The SIMATIC® S7 series supports the services FETCH and WRITE via the protocol ISO-on-TCP only in passive mode, i.e. it operates as a server and does not establish communications links spontaneously.

ISO - OSI classification
chart: ISO - OSI classification

ISO/OSI Model

7 Application Layer Fetch Read / Fetch Write
6 Presentation Layer n/a
5 Session Layer n/a
4 Transport Layer ISO-on-TCP (RFC 1006)
TCP (RFC 793)
3 Network Layer IP (RFC 791)
2 Link Layer IP (RFC 894)
1 Physical Layer Ethernet (IEEE 802.3)

Implemented Protocol Stacks

Simatic Fetch/Write, Master

Applicable Products

  • ipConv
    ipConv

    Universal protocol converter for highest degree of flexibility

  • ipConvLite
    ipConvLite

    inexpensive protocol converter for standardized application

References

  • ICESA S7
    ICESA S7, Spain

    Products: ipConvLite
    Protocol Stacks: IEC 60870-5-104, Slave Simatic Fetch/Write, Master

  • Simatic Fetch/Write - IEC 104
    Simatic Fetch/Write - IEC 104, Italy

    Products: ipConvLite
    Protocol Stacks: IEC 60870-5-104, Slave Simatic Fetch/Write, Master