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3.
Project: planning a ring structure
When planning a ring structure the following things have to be considered:
•
Set DIP-switch 4 ON, 5 and 6 to position OFF
•
The minimum response time of the slaves (min T
•
The slot time or the PROFIBUS (T
of all slaves are at the master within the slot time, even when an optical connection is broken. The
minimum slot time depends on the data rate, the length of the optical fibre and on the number of ProfiHub
F1 in the ring. It can be calculated using the formula below
T
≥ max_T
+ L
t
+ n
.
SL
SDR
LWL
LWL
max_T
:
maximum response time of the slaves.
SDR
L
:
Length of the whole optical fibre in the ring. The two longest branch lines – if there are any –
LWL
should be added to the length of the fibre optical in the ring.
:
Constant considering the bit times per km fibre optical cable (see table)
LWL
n
:
Number of ProfiHub F1 in the ring.
DL
t
:
Constant considering the delay time (in bit times) of one ProfiHub F1 (see table below).
DL
Data rate [KBit/s]
12.000
6.000
3.000
1.500
500
187,5
93,75
45,45
19,2
9,6
ProfiHub F1 User Manual v1.0.1 | September 2018 | ©PROCENTEC
) must be set to 11 bit times or higher.
SDR
) must be adjusted to a value high enough to guarantee that the answers
SL
t
.
DL
DL.
t
[Bit times/km]
LWL
240
120
60
30
10
3,33
1,66
1,66
0,33
0,17
t
[Bit times]
DL
80
40
20
10
4
3
3
3
2
2
8/26
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