Feldbus-Koppler/-Controller • 73

Fieldbus Controller 750-806

3.2.5 Data Exchange

With DeviceNet, the transmission and exchange of data is made using objects.

For a network access on the single objects, it is necessary to create a connection between the desired participants and to allocate connection objects.

The DeviceNet fieldbus Controller 750-806 can communicate via the UCMMPort (Unconnected Message Manager Port).

The UCMM-Port permits a dynamic connection via one or several connections from one or more clients.

The object configuration for the data transmission is defined by the Assembly Object. The Assembly Object can be used to group data (e.g.: I/O data) to form blocks (mapping) and send this data via one single communication connection. This mapping results in a reduced number of accesses to the network. A differentiation is made between input and output assemblies.

An Input Assembly reads data from the application via the network or produces data on the network respectively.

An Output Assembly writes data to the application or consumes data from the network respectively.

Various Assembly instances are permanently programmed (static assembly) in the fieldbus Controller.

Further information

The Assembly instances for the static Assembly are described in chapter 5.5.1.1 "Assembly Instance".

In addition to the static assembly, dynamic assembly can also be used with the fieldbus Controller. The dynamic assembly can be used to set up Assembly Instances in which process data from various application objects can be configured as required.

Further information

For information regarding the dynamic Assembly, please refer to chapter 3.2.7.4 "Dynamic Assembly".

WAGO-I/O-SYSTEM 750

DeviceNet

74 • Feldbus Coupler/Controller

Fieldbus Controller 750-806

3.2.5.1 Communication Interfaces

For a data exchange, the DeviceNet fieldbus Controller is equipped with three interfaces:

•the interface to fieldbus (-master),

•the PLC functionality of the PFC (CPU) and

•the interface to the bus modules

Data exchange takes place between the fieldbus master and the bus modules, between the PLC functionality of the PFC (CPU) and the bus modules as well as between the fieldbus master and the PLC functionality of the PFC (CPU).

Data access of the PLC functionality of the PFC (CPU) is via an application related IEC 61131-3 program and independent on the fieldbus system.

Access from the fieldbus side is fieldbus specific.

3.2.5.2 Memory Areas

The Controller uses a memory space of 256 words (word 0 ... 255) for the physical input and output data.

The Controller is assigned an additional memory space for mapping the PFC variables defined according to IEC 61131-3. This extended memory space (word 256 ... 511 each) is used to map the PFC variables behind the physical process image.

The division of the memory spaces and the access of the PLC functionality (CPU) to the process data is identical with all WAGO fieldbus Controllers. Access is via an application related IEC 61131-3 program and independent on the fieldbus system.

Access from the fieldbus side is fieldbus specific.

WAGO-I/O-SYSTEM 750

DeviceNet

Feldbus-Koppler/-Controller • 75

Fieldbus Controller 750-806

In its memory space word 0 ... 255, the Controller process image contains the physical data of the bus modules.

1The data of the input modules can be read by the CPU and from the fieldbus side.

2In the same manner, writing to the output modules is possible from the CPU and from the fieldbus side. The value of the last is written to the output while concurrent writing on an output.

Note

A concurrent writing on an output must be avoided.

Either by using instance 11 of the static assembly (see chapter 0 "

Additional Assembly Instances 10 and 11") or by using the dynamic assembly (see chapter 3.2.7.4 "Dynamic Assembly").

The PFC variables are filled in the memory space word 256 ... 511 of the process image.

3 The PFC input variables are written in the input memory space from the fieldbus side and read by the CPU for further processing.

4 The variables processed by the CPU via the IEC 61131-3 program are filled in the output memory space and can be read out by the master.

WAGO-I/O-SYSTEM 750

DeviceNet

76 • Feldbus Coupler/Controller

Fieldbus Controller 750-806

In addition, the Controller offers further memory spaces which, however, cannot be accessed from the fieldbus side:

RAM The RAM memory is used to create variables not required for communication with the interfaces but for internal processing, such as computation of results.

Retain The retain memory is a non-volatile memory, i.e. all values are retained following a voltage failure. The memory management is automatic. In this memory area, flags for the IEC 61131-3 program are filed together with variables without memory space addressing or variables which are explicitly defined with "var retain".

Note

The automatic memory management can cause a data overlap. For this reason, we recommend not to use a mix of flags and retain variables.

Code The IEC 61131-3 program is filed in the code memory. The code memory memory is a flash ROM. Once the supply voltage is applied, the

program is transmitted from the flash to the RAM memory. After an error-free start-up, the PFC cycle starts when the operating mode switch is turned to its upper position or by a start command from WAGO-I/O-PRO 32.

WAGO-I/O-SYSTEM 750

DeviceNet