ALSPA PROFIBUS Field Bus Coupler 5. PROFIBUS-DP Protocol
(09/06) Technical Manual Page 5-1
5. PROFIBUS-DP Protocol
5.1 Introduction
This section gives a brief overview of the PROFIBUS protocol when
applied to Variable Speed Drives.
5.2 PROFIBUS Protocol
The PROFIBUS board implements the PROFIBUS-DP protocol.
5.2.1 Process Data and PROFIDRIVE
CAUTION
When using the PROFIBUS interface to transfer values that
span more than one 16-bit word (e.g. a 32-bit value) the
interface does not guarantee that all members of the data set
will be sent at the same time. The user must therefore ensure
that the received value is valid.
Process data is transferred using the PROFIBUS process data
object (PPOs) packets. The PROFIBUS Profile for Variable Speed
Drives (PROFIDRIVE) contains the drive specific definition of these
PPOs. Depending on the direction of the data transfer, the PPOs
contain either control words and set points or status words and
actual values. The PPOs are sent on a regular cyclic basis at a rate
determined by the Baud rate and number of PROFIBUS devices on
the network.
Refer to the example in
2.1.6.
5.2.2
Parameter process data object types
Within PROFIDRIVE, there are five different types of PPO. Each
type of PPO is defined to contain all or some of the PPO fields.
The MVS3007-4001 PROFIBUS Fieldbus coupler only supports
either the PPO type 2 or the PPO type 4 packet, selected by DIP
switch S3-4, (see Section
3.3.2). The PPO type 4 packet is the
shorter of the two and only contains the last 12 octets of the type 4
PPO. These are shown in
Figure 5-1.
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