8.1.1 Functional Limitations With V1 / V2 Protection Devices - Siemens 7XV5550-0xA00 Series Manual

8.1.1 Functional limitations with V1 / V2 protection devices

Problems arise when cascading the Mini-Starcoupler via the RS485
interface in conjunction with devices that echo the received signal, or
that respond immediately to any received signal. The cause for this is a
bus conflict when the channel is releases with a „BYE". The „BYE" from
the pc collides with the data coming from the devices via the half duplex
RS485 bus. The termination string „BYE" is not recognised by all the
cascading Mini-Starcouplers. The channel switched through the
starcouplers is maintained until the time out.
This behaviour is known in the protection devices e.g.:
7SJ511, 7SV511, 7VE511, 7VK511.
Before applying the Mini-Starcoupler, the compatability of the devices
must be checked.
Is my device compatible?
The device may not respond immediately to the string „BYE" (without ↵).
If the device is connected with a pc, the device may not send any
characters when the string „BYE" is sent with the program „Hyper
Terminal".
Solution!
All critical devices must be connected to the first active Mini-starcoupler.
If this is not possible, the cascading of the active Mini-Starcouplers must
be with full duplex fibre optic or RS232 interfaces.
Note:
The RS232-interfaces are only point to point connections, that must be
kept as short as possible.
In the case of extended plants, an alternate cascading with fibre optic
and RS232 interfaces is recommended. In this manner, valuable fibre
optic interfaces can be saved. The fibre optic connections can cover
greater distances, while the RS232 interfaces connect two adjacent
active Mini-Starcouplers.
Page 44 from 52 Active Mini-Starcoupler 14.01.2002