CANDPSX user manual rev 2 Page 32 of 42
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8 DATA REPRESENTATION IN PROFIBUS DP
8.1 INTRODUCTION
Any standard Profibus-DP Master can exchange data with the CANDPSX module.
At startup, the Profibus-DP Master configures the communication settings of the Profibus-DP slave
nodes and then it sends them a configuration telegram. If a slave node accepts the configuration
sent by the Profibus Master, the latter shifts the slave node to the data exchange status and begins
to exchange data.
With Profibus, data exhange is carried out through a dual port consisting of two separate areas: the
input area (to Profibus-DP) and the output area (to Profibus-DP).
8.2 THE CONFIGURATION TELEGRAM
The configuration telegram provides the slave with information about the length of the Input/Output
data to be exchanged.
In general, programs for designing the Profibus-DP network also include a tool for composing the
configuration telegram, which consists of octets allowing the definition of up to 16 bytes / words of
user data to be exchanged (see § 32). Input/Output data having the same format can be combined
in a single octet. If the module detects any inconsistency between the configuration octets and its
internal configuration (determined by the programming of exchange data between Profibus-DP and
CAN) during the validation process started by the Master, a configuration error is sent to the
Master and the module is not ready to exchange data.
The CANDPSX adjust at word element the number of data in Profibus-DP.
CANDPSX can accept configuration telegrams consisting of up to 8 generic-format octets with the
following characteristics:
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