BECKHOFF BK3000 - Manual (Page 57)

Appendix
BK3xxx/LC3100 57
identifier on the bus (index/name). The OD is made up as follows:
•
Header (contains information about the structure of the OD).
• List of the static data types (list of the supported static data types)
•
Static object directory (contains all the static communications objects)
• Dynamic list of variable lists (list of the currently known variable lists)
•
Dynamic program list (list of the currently known programs)
The individual sections of the OD only have to be present if the device
actually supports the corresponding functions.
Static communications objects are entered in the static object directory and
may be predefined by the device manufacturer or be specified during the
planning of the bus system. Communications in field applications uses
principally static communications objects. PROFIBUS recognizes the
following static communications objects:
• Simple Variable
•
Array (series of simple variables of the same type)
• Record (series of simple variables of various types)
•
Domain (data area)
•
Event (a reported occurrence)
Dynamic communications objects are entered in the dynamic part of the
OD (variable list directory / program invocation directory). They may be
predefined and you can also use the application services to define, modify
or delete them during the operating phase.
PROFIBUS supports the following dynamic communications objects:
• Program Invocation
•
Variable List (series of simple variables, arrays or records)
Logical addressing is the preferred method for addressing communications
objects in PROFIBUS. This accesses the communications objects by
means of a short address, known as an index, which is a number of type
Unsigned16. This permits efficient telegrams and reduces the protocol
overhead. An index is specified in the OD for each of the communications
objects of a device. All PROFIBUS subscribers must support logical
addressing.
PROFIBUS FMS also permits the following optional addressing methods
for particular applications:
Symbolic addressing using names: in this case the symbolic name of the
communications object is transferred over the bus.
Physical addressing: here you can access any desired physical memory
address in the field devices by using the services Physical Read and
Physical Write.
Each communications object can (optionally) be protected from
unauthorized access. You can permit access to an object only with a
specific password, or restrict it to a particular device group. You can
specify the password and device group in the object directory separately
for each individual object, and you can make an entry in the object
directory to restrict the services which may be used to access the object
(e.g. read-only access).
FMS for BK3xxx Connection monitoring can be set up when acyclical connections are
established. The slave adapts to the setting desired by the master.