BECKHOFF AX2000 CANopen communication profile - Manual (Page 25)

3.4.6.2 Trigger modes
Three different trigger modes are distinguished:
l Event driven
The transmission of the telegrams is triggered by an Object-specific event. There is also the
option of masking individual bits (regardless of the Object) so that the automatic generation of
telegrams is restricted, and thus reduce the bus loading ( Þ 4.3.2.2.4 f).
l Time driven
If event driven signals put a high strain on the bus, you can determine the period of time after
which a PDO can be transmitted again via the inhibit time (Communication parameter, sub-in-
dex 03
h
)
3.4.7 Nodeguard
The Node Guarding protocol is a functional monitoring for the drive. It requires that the drive is
accessed at regular intervals by the CANopen master.
The maximum time interval that is permitted between two Nodeguard telegrams is given by the pro-
duct of the Guard Time (Object 100C
h
, Þ 4.2.1.12) and the Life Time Factor (Object 100D
h
, Þ
4.2.1.13). If one of these two values is 0, then the response monitoring is de-activated.
Node guarding is only activated when the output stage is enabled. If the drive is not accessed within
the time defined by Objects 100C
h
und 100D
h
, then Warning N04 (response monitoring) appears on
the drive, the drive is braked to a stop with the Quickstop ramp, and any other movement is preven-
ted.
The time sequence for node guarding is as shown below:
t = toggle Bit, changes its status with every slave telegram
s = status of the NMT slave status machine
Node guarding is carried out by the Master through RTR telegrams with the COB-ID, which can be
set for the slave by Object 100E
h
(
Þ 4.2.1.14).
The default value is 700
h
+ slave node address.
CANopen for AX2000/2500 25
BECKHOFF
07/2007
CANopen communication profile
NMT Master
COB-ID = ...
remote transmit request
remote transmit request
request
request
indication
indication
response
response
NMT Slave
confirm
Guard
T
ime
confirm
6..0
s
6..0
s
7
t
7
t
0
0
1
1
SPS / PLC AX2000/2500