4.3 Response Time of PLC Link
4.3.1 Response Time of One Transmission Cycle
The maximum value of one transmission cycle time (T) can be calculated using the following
formula.
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Calculation formula
(1) Ts (transmission time per unit)
Calculation
Ts = Scan time + Tpc (PLC link sending time)
formula
Tpc = Ttx (sending time per byte) x Pcm (PLC link sending byte size)
Ttx = 1/ (baud rate kbps × 1000) × 11 ms ... approx. 0.096 ms when 115.2 kbps
Pcm = 23 + (number of relay words + number of register words) x 4 (an ASCII code needs
multiplication by four)
(2) Tlt (link table sending time)
Calculation
Tlt = Ttx (sending time per byte) x Ltm (link table sending size)
formula
Ttx = 1/ (baud rate kbps × 1000) × 11 ms ... approx. 0.096ms when 115.2 kbps
Ltm = 13 + 2×n (n = No. of added units)
(3) Tso (master unit scan time)
To be checked using tool software.
(4) Tlk (link addition processing time)
Calculation
If all units have been added, Tlk = 0
formula
Tlk = Tlc (link addition command sending time) + Twt (addition waiting time)
+ Tls (sending time for command to stop transmission if link error occurs) + Tso (master unit
scan time)
Tlc = 10 × Ttx (sending time per byte)
Ttx = 1/ (baud rate kbps × 1000) × 11 ms ... approx. 0.096 ms when 115.2 kbps
Twt = initial value 400 ms
Tls = 7 × Ttx (sending time per byte)
Ttx = 1/ (baud rate kbps × 1000) × 11 ms ... approx. 0.096ms when 115.2 kbps
Tso = master unit scan time
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Calculation example
Condition
16-unit link with all units added
1
Max. unit number = 16
WUME-FPXHCOMG-02
4.3 Response Time of PLC Link
Calculation process
Ttx=0.096
Each Pcm=23+(4+8)×4=71 bytes
One transmission cycle
time (T)
T max.=Ts+Tlt+Tso
7.82×16+4.32+1
4-9