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Parameters of DB1
C.8
Example of Calculation of the Token Rotation Time
Example
Step
1
Determine the number of stations in
SINEC L2.
2
Determine the maximum possible number of
messages for each station.
3
Distinguish the messages according to type,
such as broadcast, PLC-PLC or DP connec-
tion.
4
Calculate the basic load for the individual
messages without data.
5
Determine the total data volume.
C-16
The following example is intended to clarify the calculation of the token
rotation time. It is based on a transmission rate of 500 Kbps.
Action
Implementation
The following stations are present:
DP master with station number 1
CP 541 with station number 2
CP 541 with station number 3
3 DP slaves
Both CP 541s can be simultaneously ad-
dressed as additional DP slaves.
One token message per active station
CP 541 (No. 2): one PLC-PLC connec-
tion to station 3 and broadcast
CP 541 (No. 3): one PLC-PLC connec-
tion to station 2
DP master: five DP connections
3 token messages
1 broadcast
2 PLC-PLC connections
5 DP connections
Token:
3 145 435
Broadcast:
1 480 480
PLC-PLC:
2 425 850
DP (SRD)
5 500 2500
Total load:
4265 bit times
3 DP slaves: 50 bytes (both directions
taken together)
CP 541 (No. 2):
– 20 bytes PLC-PLC connection
– 10 bytes broadcast
– 20 bytes DP connection
CP 541 (No. 2):
– 20 bytes PLC-PLC connection
– 30 bytes DP connection
Total load: 150 bytes of data
Communications Processor CP 541
EWA 4NEB 812 6188-02
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