Westermo ODW-610-F2 - Manual (Page 8)

8 6651-22611
Redundant ring via fibre optical network
Under normal operation the PROFIBUS DP data is sent over ring A.
Should a fault be detected on the fibre ring then the PROFIBUS DP data
will be carried on rings A and B.
TX RX TX RX TX RX TX RX TX RX TX RX TX RX TX RX
Master, unit Slave, unit
CH 2 CH 1
PROFIBUS DP
CH 2 CH 1
PROFIBUS DP
CH 2 CH 1
PROFIBUS DP
CH 2 CH 1
PROFIBUS DP
Ring A
Ring B
m s
… Normal operation, data exchange between PROFIBUS DP master and slave.
• Unit
M
receives PROFIBUS DP data (from a Master) at the electrical port, it converts
and transfers this master frame via the fibre ring A.
At unit
M
, the repeating of transferred frames is stopped until this transferred master
frame has returned to unit
M
via ring A.
• This master frame will be repeated through fibre ring A by all the other units. Each
of these units will also convert the master frame to PROFIBUS DP data and send it
via the electrical port.
• Unit
S
, to which the addressed Slave is connected, receives PROFIBUS DP data from
the Slave. Unit
S
converts slave data and transfers the slave frame via ring A.
The repeating of transferred frames is stopped until this transferred slave frame
has returned via ring A.
• When unit
M
receives the master frame (the same frame that has been transmitted
by this unit), or after a timeout, data conversion at unit
M
will be allowed again.
The received slave frame will be converted and transmitted at the electrical port.
• When unit
S
receives the slave frame (the same frame that has been transmitted by
this unit), or after a timeout, data conversion at unit
S
will be allowed again.
… Behaviour under faulty conditions
• Elapsed time from any kind of failure at the fibre optic network until data exchange
after a corrective action depends on total length of fibre ring.
This is typically 40–500 ms. During that time, the transferred data frames should be
seen as corrupted or missed.
Ring A
Ring A
Ring B
Ring A
Ring B
Ring A
Ring B
Ring B
Note! Ring A start up at TX (channel 1) and ring B ends up at RX (channel 1).