CANopen Programmer's Manual - Maccon.de

CANopen Programmer’s Manual 2: Network Management
Overview
Network Management Services and Objects
Network management services on the CANopen network include device state control, device
monitoring, synchronization, and emergency handling. Special communication objects, as
summarized below, provide these services.
Object Description
Network
Management
(NMT)
Synchronization
(SYNC)
This object provides services to control the state of the device, including the initialization, starting,
monitoring, resetting, and stopping of nodes. It also provides device-monitoring services (nodeguarding
and heartbeat).
Broadcast periodically by a specified device or the CANopen master to allow synchronized activity
among multiple devices. The CAN message ID of the SYNC message is 80.
Time Stamp Broadcast periodically by a specified device or the CANopen master to allow devices to
synchronize their clocks.
Emergency Transmitted by a device when an internal error occurs.
Network Manager Node
Normally, a single node (such as a PC) is designated as the network manager. The network
manager runs the software that issues all NMT messages. The network manager node can be the
same node that runs the CANopen master application.
General Device State Control
State Machine
Every CANopen device implements a simple state machine. The machine defines three states
(described below). The network manager application uses NMT messages to interact with the
state machine and control state changes.
Device States
The following states are defined for Copley Controls CANopen amplifiers:
State Description
Pre-operational Every node enters this state after power-up or reset. In this state, the device is not functional, but
will communicate over the CANopen network. PDO transfers are not allowed in pre-operational
state, but SDO transfers may be used.
Operational This is the normal operating state for all devices. SDO and PDO transfers are both allowed.
Stopped No communication is allowed in this state except for network management messages. Neither
SDO nor PDO transfers may be used.
State Control Messages
One use of NMT messages is to control state changes on network devices. The following NMT
messages are sent by the network manager to control these state changes. Each of these
messages can be either sent to a single node (by node ID), or broadcast to all nodes.
Message Effect
Reset Causes each receiving node to perform a soft reset and come up in pre-operational state.
Reset
communications
Causes each receiving node to reset its CANopen network interface to power-on state, and enter
pre-operational state. This is not a full device reset, just a reset of the CANopen interface.
Pre-operational Causes the receiving node(s) to enter pre-operational state. No reset is performed.
Start Causes the node(s) to enter operational state.
Stop Causes the node(s) to enter stopped state.
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