Bus Access; Token Passing; Master/Slave Polling; Communication Types - ProSoft Technology ProLinx PDPM Protocol Manual

Functional Overview
Protocol Manual
Standard
Transmission equipment (Physical) EIA RS-485
Transfer procedure
Bus topology
Bus cable type
Connector
Number of nodes on the bus

2.2.1 Bus Access

Two different bus access procedures handle the various communication
requirements for the PROFIBUS DP Master topology:


Token Passing


Polling
2.2.2 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.

2.2.3 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.
2.3

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)
Page 8 of 70
EIN 501 70
DIN 19245
IEC 1158-2 (through link or coupler)
Fiber Optic Cable (not available)
Half-duplex
Linear bus with active bus termination
Shielded twisted pair conductors
9-pin D-Sub
Max: 32 with no repeaters
Max: 125 with 3 repeaters in 4 segments
PDPM ♦ ProLinx Gateway
PROFIBUS DP Master
ProSoft Technology, Inc.
June 24, 2013