User`s manual

12-13
M-net (Master Station) Function
12
12-3 Communication time and communication timing
(1) Time required for transmission
This section shows how to calculate the time required for one cycle of data transmission. One cycle of
data transmission means the time required for the M-net to communicate between the master station
and all slave stations.
One cycle time for transmission T=
+ 15P + α (unit: ms)
19.2
20N+60P
T=
+ 15x7+0.2=193.7 (ms)
19.2
20x64+60x7
(2) Connection sequence time
The connection sequence is a test communication to check whether the master station can
communicate correctly with the slave stations.
- If you turn ON the start relay in the PC program, the test communication will start.
- Up to 265 ms are required to execute the connection sequence. (Even if only one slave station is
connected, the connection sequence will test the communication with all seven slave stations.)
- When designing a PC program, take the connection sequence time into account.
ON
01 02 03 04 05 06 07
01 02 03 04 05 06 07 01
Normal sequence
(one cycle)
Start relay
Communication
process
Connection sequence
(up to 265 ms)
(3) Time for data exchange with a PC
Shown below are the times required for data exchange between a PC and various modules. The PC
scan time for the master and slave stations will get longer as the data exchange time becomes longer.
Approx. 0.2 ms *
Approx. 1 ms
Approx. 6 ms
Approx. 0.1 ms
Approx. 6 ms
Approx. 0.2 ms
* This is the time when the JW-34KB/36KB/38KB is used as the basic rack panel. When
using the JW-24KB/26KB/28KB, the data exchange time will be approx. 1 ms.
PC model
Data exchange time
(when 64 bytes are transmitted)
JW-32CUM1
JW-31CUH1/32CUH1/33CUH1/33CUH2/33CUH3
JW-31CUH/32CUH/33CUH
JW20/20H
W70H/100H
JW50/70/100
JW50H/70H/100H
J-board (Z-311J/312J)
J-board (Z-511J/512J)
JW30H
Approx. 0.2 ms
(4) Communication lag time
The following time lag occurs when receiving data over the M-net communication.
ON
ON
Master station PC input
I/O processing
I/O
processing
I/O
processing
I/O
processing
I/O
processing
1 PC scan
Master station PC
Operation
Operation
Operation
Operation
Communication
Slave station PC
Slave station PC output
Communication lag time
N: Total number of bytes communicated (unit: byte)
P: Number of slave stations connected (do not count the master station)
a: Time required for the master station to exchange data with a PC (- See section (3) below.)
19.2: Transfer speed (38.4 when the transfer speed is set to 38.4 k bits/s)
[EX] When a JW30H (JW-32CUM1) is used as a master station, there are 7 slave stations, and 64
bytes are communicated in one cycle.