how to use LAS Back up

[kourosh]

Hello all

I would like to know whether all the ABB device support LAS Back up capability and which condition is necessary to use this ability?

Thanks in advance.

[Mike ONeill]

The device datasheet will confirm back-up LAS capability; it's usually an extra-cost option or provided on the premium devices.

It isn't something that you will go out of your way to use, but if for some reason your primary H1 interface card (linking device) gets screwed and you didn't have a redundant pair, then the back-up LAS will keep any CIF going within that segment, assuming there is still power and cable continuity.

[rezabejd]

I would like to know whether all the ABB device support LAS Back up capability.
If you go to fieldbus.org > End User Resources > Registered Products and search for ABB, you will get a listing of all the devices they have registered.

I get a listing of 17 products (http://www.fieldbus.org/index.php?option=com_mtree&task=search&Itemid=324&ffbstatus=Registered&ffbmfg=ABB+Automation+Products+GmbH&ffbcategory=)which includes Linking Devices and power conditioners. For field devices, the profile (http://www.fieldbus.org/index.php?option=com_mtree&task=viewlink&link_id=650&ffbstatus=Registered&Itemid=324) details whether the device has link master capabilities by the heading "H1 Device Class".

By the way, if you are using redundant H1 interface cards or redundant linking devices, AG-181 (Systems Engineering Guide) doesn't encourage random or blanket use of BLAS in field devices. The capability is rarely invoked (both H1 interface devices would have to fail) and it consumes download time every time you make a change on the segment schedule. AG-181 says your default should be "BLAS capability off / disabled" unless you have a specific case where you've determined it's warranted.

[agupta]

Any LM (Link Master) capable device can become LAS. Therefore, as long as there are two LMs, there is one backup LAS. The lowest address available LM becomes the LAS. If it fails, then the next lowest address LM becomes LAS. You do not have to configure anything except the addresses, for this backup function.
You should assign the addresses, such that the most capable LM device has the lowest address and the next capable LM device has the next address.The H1 interface to the Host system should usually be the lowest address device, so that it is the primary LAS. If the interface is not redundant, then a LM field device works as the backup.
Make sure that the host system downloads the LAS schedule to all LM devices.