Profibus Actuator Control Profibus DP Option Card Installation Manual

Profibus DP Mk2 Option Card Installation Manual
4.3.1 Flying Redundancy Slave to Master Connection
Primary Master
Backup Master
n
64+n
Primary
Backup
Slave
FR
Fig 10: Profibus DP (Mk2) Flying Redundancy Connection
With FR (Flying Redundancy) the aim is to protect against a failure of the Profibus Interface. The data
highway is considered to be more reliable than the connection interface. There is a single data
highway and both the Profibus card inputs are connected to it. The card must be set to FR mode and it
then adopts a fixed offset of 64 between the set address (used for primary communication) and the
backup communication address.
When the card is powered ‘on’, Channel 1 will be the Primary channel. If the card does not enter
Configuration Mode within 1 second (because there is no Master present) then Channel 2 will take
over as Primary, once again if there is no communication within 1 second, then it will revert to Channel
1 and now it will wait 2 seconds before Channel 2 assumes Primary status. The switch over time will
increase by a factor of 2 each time until it reaches its maximum of 32 seconds. It will continue to
switch channels using a 32 second switch over time until one channel receives PLC messages.
In the event of a failure of the Primary channel, the Backup automatically changes to use the Primary
address. Hence for all control purposes the Master only uses the Primary address. The Backup
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 address it will accepted, but not actioned. The data exchanged
between the Master and the Primary includes information on the status of the device and hence the
availability of a Backup should the Primary fail.
Single Data Highway, two communication ports
Channel 1 is Primary on power up
Default method is SR mode, to achieve FR the associated parameter must be altered
Fixed offset of 64 between Primary and Backup addresses
Backup automatically adopts Primary address if Primary fails.
V0 cyclic Commands to Backup ignored
Reports the status of Primary and Backup to the Master
Configuration and Parameterisation changes only over the Primary address
18 of 66 Publication S420E V3.0 Issue 01/05