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MELSEC-
A
3 SPECIFICATIONS AND FUNCTIONS
Transient transmission
(1) When master module is AJ61BT11, A1SJ61BT11, AJ61QBT11 or
A1SJ61QBT11
(a) Calculation expression
Details Calculation expression (Unit: ms)
Master module D75P2
(write)
{SM
2 + LS 6 (number of write points
*1
+ 16)/72
*2
LS +
bps constant}
N
Master module D75P2
(read)
{SM
2 + LS 5 (number of read points
*1
+ 16)/16
*2
LS +
bps constant}
N
*1: Set in word unit
*2: Rounded up to the one place
SM : Scan time of master module sequence program
LS : Link scan time (refer to the Master Module User's Manual)
: Number of read points
1 to 120points 121 to 240points 241 to 360points 361 to 480points
LS LS 2 LS 3 LS 4
bps constant
156kbps 625kbps 2.5Mbps 5Mbps 10Mbps
LS LS 2 LS 4 LS 6 LS 7
N : Number of simultaneously executed commands
(b) Calculation example
The following example calculates the transmission delay time taken when
"
Md.30
Machine feed value" (2 words) is read from the D75P2.
When SM is 20ms, transmission speed is 10Mbps, and only one D75P2 is
connected
LS: 1.8ms (for the calculation expression, refer to "(2) Calculation example in
Cyclic transmission")
Transmission delay time = {SM
2 + LS 5 + LS + (2 +16)/16 LS + LS 7} 1
= {20
2 + 1.8 5 + 1.8 + (2 +16)/16 1.8 + 1.8 7} 1
= 40 + 9 + 1.8 + 3.6 + 12.6
= 67[ms]
Therefore, the read machine feed value is the data after 67ms.
However, when data is read from the buffer memory whose update timing is at
56.8ms intervals
*1
, data after a maximum of 67 + 56.8 = 123.8ms is read as
shown below depending on the read timing.
*1
Md.37
update timing is at 910ms intervals.
D75P2 update timing
56.8ms 56.8ms 56.8ms 56.8ms
Md. 30 Machine feed value
1)
Read
execution
Read
complete
67+1) (ms)