ETIC AFO485, Руководство пользователя, Страница: 23 / 36

AFO485 and RFO485 USER MANUAL ref 9011509-01 Page 23
3.8.2 Range of repeaters in a failsafe ring
Taking into account the algorithm of the
failure detection used, the maximum size
of the ring is determined in three stages :
Step 1 : The distance D1 between 2
repeaters can not exceed the distances
marked in the tables in section 3.7.1,
these distances depend on the type of
RFO485 and the fibre optic cable used.
Step 2 : Moreover, the distance D1 between 2 repeaters can not exceed
the values in the table below.
Maximum length of a segment of the ring
Kb/s D1 in Km
9,6 20,0
19,2 10,0
38,4 5,0
93,75 2,1
57,6 3,5
115,2 1,7
187,5 1,0
500 0,4
1500 0,1
Step 3 : In addition, the total length of the ring can not exceed the value
D2 given by the formulas below.
If the latency time of the ring is greater than two character lengths:
D2 = 200 X (20-N) / R
If the latency time of the ring is greater than one character length
:
D2 = 200 X (10-N) / R
N= Number of repeaters
R (Kb/s) = data rate of the asynchronous link (between 1,2 and 1500)