ProSoft Technology PTQ-PDPMV1 - Manual (Page 250)

Reference PTQ-PDPMV1 ♦ Quantum Platform
User Manual PROFIBUS DP Master Network Interface Module for Quantum
Page 250 of 306 ProSoft Technology, Inc.
August 12, 2014
Bus Access
Two different bus access procedures handle the various communication
requirements for the topology:
 Token Passing
 Polling
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.
Master/Slave Polling
Master/slave polling guarantees a cyclic, real-time based data exchange
between the station with transmission rights, the active station, and its
subordinates, the passive stations. In this case, the Master is able to pass data to
the slave and/or receive data. The services in layer 2 (field-bus data link in ISO-
OSI reference model) organize this communication.
9.2.4 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
 the number of configured inputs and outputs is correct