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MELSEC-QnA
15 FUNCTIONS (FUNCTION VERSION B OR LATER)
15.8.4 Link scan time
The link scan time (LS) when the remote I/O net mode is used can be calculated using
the following expression.
LS = BT {25.0 + (NI × 4.0) + (N × 28.0) + (ni × 4.0)} + ST
+ {Number of communication faulty stations × 48 × BT × Number of retries}
[µs]
BT : Constant (transmission speed)
Transmission speed 156kbps 625kbps 2.5Mbps 5Mbps 10Mbps
BT 51.2 12.8 3.2 1.6 0.8
NI : Last station number (a multiple of 8)
N : Number of connected stations
ni : Total number of occupied stations
ST : Constant
ST = 200 + (ni × 20)
: Only when there exist communication faulty stations.
The following shows a difference in link scan time between operations using the
remote I/O net mode and the remote net mode (conventional mode).
10 20 30 40 50 60 64
0
1000
2000
3000
4000
: In remote net mode (theoretical value)
: In remote I/O net mode (theoretical value)
Number of remote I/O stations station
LS s
Fig. 15.4 Link scan time
15.8.5 Precautions
Set the remote I/O station numbers sequentially. Failure to do so will detect the omitted
station as an error, affecting the link scan time.