Profibus Installation Manual
36
6.5 Single Highway Dual Channel – FR Mode
On either the Simple or RedCom dual channel card
the mode for communications may be set to FR (Flying
Redundancy) in some cases. This will require the card’s GSD
file to be changed or the parameter value altered by a PDM
or FDT utility.
Redundancy
SR is the default mode; it must be altered for FR mode.
In FR mode there is one highway and a single PLC can be
used. The two channels on the card each have an address
offset by 64. One channel is in Primary mode and uses the
base address whilst the other is in Backup mode using the
base address plus 64. As with SR mode, the card is waiting
for a communication message on the channel that is in
Primary mode and the two channels will switch their mode
whilst searching for comms. There is no discrimination
between Channel 1 and Channel 2 to determine which is
in Primary mode. The two channels will both try to adopt
Primary mode. The difference here is that the PLC can
communicate with the backup using a different address.
When using either type of dual channel card in FR mode the
following must be set up:
Address
The two channels have address offset by 64. The address
can be set using the Accent software directly with the
actuator (free from www.Rotork.com) or using the setting
tool. The address can also be set over the highway using a
Class 2 master.
Baud Rate
This is selected by the PLC, both channels adopt the same
baud rate.
Slave Configuration
One of the 10 configurations for the slave must be chosen.
Both channels will use the same configuration setting.
Configuration can only be carried out on the Primary
channel.
Basic Parameterisation
The basic parameters such as deadband and motion inhibit
time can be set using either the GSD file or a suitable PDM
or FDT utility. The default settings will be suitable for most
systems. Both channels will adopt the same settings.
Parameterisation can only be carried out on the Primary
channel.
IDATA4 Bit 5 indicates the channel status and will show if
the channel in communication is the Primary or Backup.
FR
Highway 1
Master PLC Standby PLC
Primary
address # = n
Backup
address # = 64+n
Probus Card
Fig. 21: Flying Redundancy – One highway redundancy
FR Mode -
•
Primary is offset from Backup address by 64.
•
When the card is powered ‘on’ Channel 1
will be the Primary channel. After power up
the card will seek a master to communicate
with by alternating the channel 1 and 2
between Primary and Secondary mode. The
switch over time increases with each change
to a maximum of 32 seconds. The card will
continue to switch channels using a 32
second switch over time until one channel
receives PLC messages. The channel addresses
alternate at this point.
•
The PLC need not wait for a particular channel
to be in Primary mode before starting
communications.
•
If the Primary channel fails the Backup will
automatically adopt Primary address and wait
for messages from the master.
•
The Backup channel address can be used for
exchanging data but any commands to move
the actuator directed to the backup address
will be ignored.
•
If a configuration message is sent to the
Backup address that is different to the one
sent to the Primary it will be accepted, but not
carried out.
Profibus DP Communication
A4US
US
A4
US A4
US
A4