Siemens SITRANS F M TRANSMAG 2, Руководство по эксплуатации, Страница: 95 / 114

Profibus Communication
B.3 Cyclic Data Traffic
SITRANS F M TRANSMAG 2
Operating Instructions, 11/2009, A5E00102775-07
93
Note
The specified immunity and radiated emission are only guaranteed if the bus shielding is
fully effective. This includes connecting the shields to the metal connections of Transmag
2, but also laying the shields to the terminal compartment, distributor, DP/PA coupler or
DP/PA link.
Terminators
To ensure trouble-free communication, the PROFIBUS must have a bus terminator at both
ends. This is usually already provided by the coupler or link at the control system end. An
additional bus terminator must be fitted at the remote bus end.
B.3 Cyclic Data Traffic
Cyclic data transmission serves for fast exchange of useful data between a class 1 master
(control system or PLC) and the slave (SITRANS F M).
Up to four different measured values (= modules) can be transmitted cyclically from the
device to the control system as input data in one telegram with the "Data_Exchange" service.
The following measured values are available for selection in the given order:
1.
Flow (volume or mass flow)
2. Totalizer (volume or mass) net
3. Totalizer (volume or mass) forwards
4. Totalizer (volume or mass) reverse
The output data are sent to the device with the cyclic request telegram. The number and
type of actually transferred data can be determined with the aid of the configuration data
(see )
Acyclic data traffic
Acyclic data transmission is mainly used for remote control of the device, i.e. for transmitting
parameters during commissioning, maintenance, batch processes or for displaying other
variables which do not participate in the cyclic useful data traffic.
Acyclic accesses can be made by a class 1 master (C1 connection) or a class 2 master (C2
connection). Sitrans F M supports up to four simultaneous C2 connections.
The more than 300 parameters including address (Slot and Index), format, value range, start
value and attributes are stored in an object list "Obj80C4.rtf" which will be provided on
request.
Acyclic operation takes place preferably with the SIMATIC PDM software package and a PC
(compatible with the industrial standard) or programming device (see section 5.1).