4
FUNCTIONS
4.1 Cyclic Transmission Function
4.1.6 Cyclic transmission punctuality assurance
4
- 23
1
O
V
ER
VI
E
W
2
SYST
EM
CO
NF
IG
URA
T
IO
N
3
SPECI
F
IC
A
T
IO
N
S
4
F
UNCT
IONS
5
PREP
ARA
T
IO
N AND
SET
UP
6
P
A
RAM
E
T
E
R
SET
TI
NG
7
PRO
C
ESSI
NG
T
IM
E
8
PRO
G
R
AM
M
ING
4.1.6
Cyclic transmission punctuality assurance
This function keeps the link scan time constant by making each station to send the
specified number of transient transmissions within one link scan.
POINT
(1) Use this function to eliminate the fluctuation in link scan time, which is caused
by transient transmissions. (Optimum cyclic transmissions are available.)
Note that, if the network line status is unreliable, the cyclic transmission
punctuality may not be ensured.
(2) To keep the link scan time constant even if the network line status is
unreliable, use the constant link scan function.
Section 4.1.7 Constant link scan
(3) While this function is used to keep the link scan time constant, the
transmission delay time is not kept constant by this function.
The transmission delay time is affected by a factor such as a prolonged
sequence scan time.
(4) If the punctuality assurance setting is enabled, the link scan time is constant
but longer than the case of no punctuality.
(1) When the punctuality assurance setting is disabled
If each of stations sends transient data several times in one link scan, the link scan
time fluctuates and the punctuality of cyclic transmission cannot be ensured.
Figure 4.30 Without punctuality assurance
Control station
No.1
Normal station
No.2
Normal station
No.3
Normal station
No.4
Cyclic transmission
Transient transmission
<When many transient transmissions are sent among stations during one link scan>
<When no or a few transient transmissions are sent among stations during one link scan>
Hardly affects the link scan time.
The transient transmissions change the link scan time.
Link scan time
Link scan time
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