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5 DATA LINK PROCESSING TIME
MELSEC-QnA
5.2 Link Scan Time
The link scan time of CC-Link is calculated as follows using:
[Link scan time (LS)]
LS = BT {29.4 + (NI × 4.8) + (NW × 9.6) + (N × 32.4) + (ni × 4.8) + (nw × 9.6)} + 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 in a, b, and c
(including number of occupied stations and excluding number of reserved stations)
NW : Last station in b and c
(Including number of occupied stations and excluding number of reserved stations)
It should
be the
multiple
of 8.
Last station number 1 to 8 9 to 16 17 to 24 25 to 32 33 to 40 41 to 48 49 to 56 57 to 64
NI, NW 8 16 24 32 40 48 56 64
N : Number of connected stations (excluding the number of reserved stations)
ni : a + b + c (excluding the number of reserved stations)
nw : b + c (excluding reserved stations)
ST : Constant (It should be the largest value in items
1
to
3
below. When b = 0, ignore item
2
and,
when c = 0, ignore item
3
.)
1
800 + (a × 15)
2
900 + (b × 50)
3
When c
26: 1200 + (c × 100)
When c > 26: 3700 + {(c - 26) × 25}
a : Total number of occupied stations for remote I/O stations
b : Total number of occupied stations for remote device stations
c : Total number of occupied stations for intelligent device stations (including local stations)
: Only when there exist stations with faulty communication (including error invalid stations and
temporary error invalid stations)
(Example) When the transmission speed is at 2.5 Mbps in the following system configuration:
Station No.2
1 1
Station No.3 Station No.4
2
Station No.6
2
Station No.8
1
Station No.9
3
Station No.13
1
Remote I/O
station
Local
station
Local
station
Remote device
station
Remote device
station
Remote I/O
station
Remote I/O
station
Remote I/O
station
Master
station
Station No.1
1
1: 1 station occupied 2: 2 stations occupied 3: 4 stations occupied
BT = 3.2 ST = 1700
NI = 13
16
1
800 + (4 × 15) = 860
NW = 12
16
2
900 + (4 × 50) = 1100
N = 8
3
1200 + (5 × 100) = 1700
ni = 13 a=4 b=4 c=5
nw = 9
LS = 3.2 {29.4 + (16 × 4.8) + (16 × 9.6) + (8 × 32.4) + (13 × 4.8) + (9 × 9.6)} + 1700
= 3836.96 [µs]
= 3.84 [ms]