Operating instructions

4. How to Control the Frequency Converter

4.1. DeviceNet Process Control Modes

This section describes two of three possible process control modes: Polling and Change of State

(COS).

The third FC control mode uses the acyclical mode Explicit Messaging via the Standard DeviceNet

Control Supervisory object CLASS 29H. The Control Supervisory object is described within the

DeviceNet Object Classes

section,

How to Access the Parameters

chapter.

4.1.1. Polling

This is a classical Master-Slave connection and

the standard DeviceNet operation mode. The

master controls the data exchange by sending

cyclical poll-requests to the connected slaves,

and the slaves answers by sending a poll-re-

sponse to the master. The master can control

and monitor the frequency converter by poll-

ing the DeviceNet or Danfoss objects (I/O In-

stances).

POLLED I/O

Master → slave

CTW MRV

Slave → master

STW MAV

4.1.2. Change of State, COS

This an event-controlled operation mode used to minimize network traffic. Messages are trans-

mitted only if a defined state or value has changed. The condition for triggering a COS message

is determined by the insertion of COS-filters (parameters 10-20 to 10-23), for each bit in the

different PCD-words. The filter acts like a logical AND-function: If a bit in the filter is set to “1”,

the COS-function triggers upon a change to the corresponding bit for the PCD-word.

FC 100/ 200/ 300 DeviceNet 4. How to Control the Frequency Converter

MG.33.D3.02 - VLT

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