Instructions

Basic Operation 15
Doc: HMSI-27-306, Rev. 3.11Anybus Communicator PROFIBUS User Manual
2.3 Subnetwork Protocol
2.3.1 Protocol Modes
The Anybus Communicator features three distinct modes of operation regarding the subnetwork com-
munication, called “Master Mode”, “DF1 Master Mode” and “Generic Data Mode”. Note that the pro-
tocol mode only specifies the basic communication model, not the actual subnetwork protocol.
•Master Mode
In this mode, the gateway acts as a master on the subnetwork, and the serial communication takes
place in a query-response fashion. The nodes on the network are not permitted to issue messages
unless they have been addressed by the gateway first.
For more information about this mode, see “Master Mode” on page 16.
• Generic Data Mode
In this mode, there is no master-slave relationship between the subnetwork nodes and the gate-
way; any node on the subnetwork, including the gateway, may spontaneously produce or con-
sume messages.
For more information about this mode, see “Generic Data Mode” on page 16.
• DF1 Master Mode
In this mode, the gateway acts as a master on the subnetwork, using the DF1 protocol. The serial
communication takes place in a query-response fashion. For information about this mode, see
“DF1 Protocol Mode” on page 46.
2.3.2 Protocol Building Blocks
The following building blocks are used in Anybus Configuration Manager to describe the subnetwork
communication. How these blocks apply to the three protocol modes will be described later in this doc-
ument.
•Node
A node represents a single device on the subnetwork. Each node can be associated with a num-
ber of transactions, see below.
•Transaction
A transaction represents a complete serial telegram, and consists of a number of frame objects
(see below). Each transaction is associated with a set of parameters controlling how and when to
use it on the subnetwork.
• Commands
A command is simply a predefined transaction stored in a list in the Anybus Configuration Man-
ager. This simplifies common operations by allowing transactions to be stored and reused.
• Frame Object
Frame Objects are low level entities used to compose transactions (see above). A frame object
can represent a fixed value (a constant), a range of values (limit objects), a block of data or a cal-
culated checksum.