Process Data Communication - Altivar Process ATV900 Manual

Basics

Process Data Communication

Description
Process Data Objects (PDO) are used for real-time data exchange of process data such as actual and
reference values or the operating state of the device. Transmission is fast because the data is sent without
administration data and data transmission acknowledgment from the recipient is not required. Each PDO
can be enabled or disabled independently using the bit 31 (valid bit) in subindex 01 hex of the respective
communication object.
PDO1 Details
The first PDO is by default compliant with the PDO1 of the Velocity mode of the CiA402. It is asynchronous
and contains two data: the control word (6040 hex, CMD) and the target velocity (6042 hex, LFRD) for the
output (from Master to Device) and the status word (6041 hex, ETA) and the control effort (6044 hex,
RFRD) for the input (from Device to Master).
PDO2 Details
The second PDO set (PDO2) is deactivated by default and can be fully configurable (1 to 4 words of the
user choice). It is reserved for adjustments and for additional control and monitoring functions.
PDO3 Details
The third PDO set (PDO3) is reserved. Deactivated by default, it cannot be configured and comprises:
RPDO3 (receive), containing four output (from Master to Device) words of the communication scanner

NC1 to NC4
TPDO3 (transmit), containing four input (from Device to Master) words of the communication scanner

NM1 to NM4
Transmission Mode
By default, the three PDOs are asynchronous, although the transmission mode of each PDO can be
reconfigured by the user in accordance with requirements:
Asynchronous mode (255): The transmit PDO is only sent when the value of its data changes. In this

mode, the inhibit time and event timer can be modified in order to adjust the PDO transmission
frequency on the bus.
Cyclic synchronous mode (1...240): The transmit PDO is sent each time a synchronization object

(SYNC) is received or when a preconfigured number of synchronization objects (from 1 to 240) is
received.
Acyclic synchronous mode (0): The transmit PDO is sent each time the value of its data changes, but

only during the synchronous window authorized by the next synchronization object (SYNC).
Synchronization Object
The synchronization object (SYNC) is sent cyclically by the CANopen master. It does not contain data and
its frame is limited to its unique COB ID identifier (080 hex). The purpose of this object is essentially to
authorize synchronous communication modes for CANopen slaves.
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NHA80945 04/2017