●
The minimum response time of all slaves (min T
SDR
) has to be set to a value
of 11 bit times (basic setting) or more. In the event of continuous communication
faults, this value has to be verified.
●
The Profibus slot time (T
SL
) must be set as to ensure that on request of the
master, the response of the slaves arrives at the master within the slot time -
even in the event of a fault in the fibre optic cable.The minimum slot time in bit
times depends on the data rate, the total length of the fibre optic cable and the
number of actuators used within the loop.
Calculation of slot time:
T
SL
≥ max_T
SDR
+ L
FO
* t
FO
+ n
DL
* t
DL
T
SL
Slot time
max_T
SDR
Maximum response time of the slowest slave in bit times.In the table below, the
values of the AC 01.2 have been entered.
L
FO
Overall cable length of the FO cable used within the loop in km.
If bus segments start from the loop couplers, which have been extended beyond the
maximum electrical cable lengths using FO couplers or repeaters, the two longest
bus segments should be added to the FO cable length within the loop.
t
FO
Constant that accounts for the bit times per FO cable (refer to table)
n
DL
Number of actuators used within a loop
t
DL
Constant that accounts for the running time of an FO module in bit times (refer to
table)
max_T
SDR
t
DL
[bit times]t
FO
[bit times/km]Data rate [kbit/s]
2010301,500
15410500
1533.75187.5
1531.87593.75
1530.90945.45
1520.38419.2
1520.1929.6
11
Network topologies