Error Control Services; Configuration Control Services - Omron C200HW-CORT21-V1 Operation Manual

Communication
Boot-up object
Pre-Operational state
Operational state
Stopped state

1-3-4-2 Error control services

Heartbeat
Node Guarding
Life Guarding

1-3-4-3 Configuration control services

Before entering the Pre-Operational state, the standardised boot-up object is
transmitted. This object indicates to the network that the respective node has
completed its initialisation and will enter Pre-operational state.
After power-on and internal initialisation, every device autonomously enters
the Pre-Operational state. In this state the node may be configured and
parameterised via SDO accesses (e.g. by using a configuration tool); no
PDO communication is allowed.
An NMT Master may switch a specific node, or all nodes simultaneously, to
the Operational state. In this state, all communication objects are active.
PDO transfers are possible, as well as object dictionary accesses via SDO
messages.
By switching a device into the Stopped state, it is forced to stop all PDO and
SDO communication.
The CANopen protocol has two error control services:
•
Node / life guarding
•
Heartbeat
In any node, these two services are mutually exclusive. The service that is
started first from the boot-up phase, will be active. In case the heartbeat
service is disabled, it is possible to start Node / Life guarding.
A Heartbeat Producer transmits the Heartbeat message cyclically with the
frequency defined in the Heartbeat Producer time object. One or more
Heartbeat Consumer may receive this message. The relationship between
producer and consumer is configurable via object dictionary entries.
The Heartbeat Consumer monitors the reception of the Heartbeat within the
Heartbeat consumer time. If the Heartbeat is not received within this time, a
Heartbeat event is generated to notify the receiving node's application.
With the node / life guarding mechanism, the NMT master polls the NMT
Slaves at regular intervals. The slaves respond with their current node state.
If a node state does not correspond with the expected state stored in the
NMT master, or the slave does not respond at all within a configurable time
frame, the respective node will be considered faulty. This process is known
as Node Guarding.
To check if the NMT Master is still alive, the slaves monitor internally if the
master sends the Node Guarding message within the configured life-time.
This is known as Life Guarding.
The preferred error control service is Heartbeat. This mechanism reduces the
bus load and does not make use of remote transmission request message
frames.
Configuration control services are used for up- and downloading of
configuration data from / to a module in the network. Refer to section 1-3-2
for details about how modules are accessed.
Section 1-3
15