ProSoft Technology MVI69-PDPMV1 - Manual (Page 161)

MVI69-PDPMV1 ♦ CompactLogix or MicroLogix Platform Reference
PROFIBUS DPV1 Master User Manual
ProSoft Technology, Inc. Page 161 of 225
July 8, 2011
6.2.1 Bus Access
Two different bus access procedures handle the various communication
requirements for the PROFIBUS DPV1 topology:
 Token
Passing
 Polling
6.2.2 Token Passing
Token passing ring is the basis for communication between the more complex,
active stations. All stations have the same rights in that a token is passed from
station to station in a logical ring. The token is passed to each station with a
maximum, definable token cycle time. A station is given transmission rights for
the duration of time that it has the token.
6.2.3 Master/Slave Communication Phases
The communication between the Master and the slaves is split up into the
following phases:
 Parameterization and configuration phase
 Usable data transfer phase
Before a DP slave can be integrated into the usable data transfer phase, the
parameterization and configuration phase runs a device identification test that
verifies that the planned configuration matches the actual device configuration for
each slave in the PROFIBUS network. The test verifies that:
 the device is actually there
 it is the right type of device
 the address, which is set on the device, matches the station address on the
bus
 the formats, telegram length information, and bus parameters are correct
and
 the number of configured inputs and outputs is correct.
6.2.4 Communication Types
In addition to point-to-point data transfer, the PROFIBUS protocol can also
handle the following types of communication.
 Broadcast
communication:
An active node sends an unacknowledged message to all other nodes
(Master and slaves)
 Multicast communication (control instructions)
An active node sends an unacknowledged message to a group of nodes
(Master and Slaves)