4-6. Communication Times
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4-6.Communication Times
The communication time is the time required for communications to be completed in a network.
This depends upon the transmission cycle, transmission timing and the time needed for CPU processing(CPU scan
time).
1. Transmission Cycle Time
Ttc = STsti + 0.6 ms
= Tst1 + Tst2 +•••••+ Tsti + 0.6 ms
= (Tpr + Tmg + Tpc1 + Tdt1) + (Tpr + Tmg + Tpc2 + Tdt2) + •••
••• +(Tpr + Tmg + Tpci + Tdti) + 0.6 ms
where :
Ttc = Time needed for one transmission cycle
Tsti = Time needed for token processing at station i
Tpr = Time needed for basic token processing at each station
The Tpr value at each station is fixed as :
Tpr = 0.6 ms
Tmg = Time needed for basic token management at each station after transmission operation
1. When 2 to 31 stations are linked in the network
The Tmg value at each station should be calculated as :
Tmg = 0.4 ms
2. When 32 stations are linked in the network
The Tmg value at each station should be calculated as :
Tmg = 0 ms
Tpci = Time needed for P/W PC Link processing at a station in PC Link Mode
[station number "i"(UNIT NO. "i")]("i" = 0 to 16).
Tdti = Time needed for Data Transfer processing at station i (UNIT NO. i).
In the W Type(Wire) Link System, a token is passed
from one station to the next in sequential manner.
One transmission cycle is specified as the time
required for “one token(mastership) to be passed
from one station to the next ,etc., unitl it returns to
the same station.”
Notes :
The time needed for one transmission cycle is called
the transmission cycle time.
The total transmission cycle time(Ttc)is calculated
by adding the time needed for each station token
processing cycle as shown in the following equation :
[One Transmission Cycle]
When N stations are connected in a network
N = 1 to 32
Token Processing time (Tst1)
• Basic token process time(Tpr)
• P/W PC Link Process time(Tpcl)
• Data Transfer process time(Tdtl)
Management
time
(Tmg)
Token
received
Token
passed
One Transmission Cycle
1st
station
process
the taken
2nd
station
process
the taken
3rd
station
process
the taken
Nth
station
process
the taken
• Refer to the figure shown on the right.
• The transmission cycle of the W Type(Wire)
Link System is not synchronous with the
CPU scan.(Asynchronous)
