ProSoft Technology 5105-103M-PDPS - Manual (Page 111)

5105-103M-PDPS ♦ ProLinx Gateway Reference
IEC 60870-5-103 Master to PROFIBUS Slave Gateway User Manual
ProSoft Technology, Inc. Page 111 of 144
November 24, 2010
Bus Access
Two different bus access procedures handle the various communication
requirements for the PDPS 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.
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).
Master/Slave Communication Phases
The communication between the Master and the Slaves takes place in 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 station address set on the device matches the station address in the bus
configuration
the formats, telegram length information, and bus parameters are correct
and
the number of configured inputs and outputs is correct.