Cautions On Program Creation - Mitsubishi Electric FX3U-232-BD User Manual

FX Series PLC User's Manual - Data Communication Edition
N:N Network
7.4

Cautions on Program Creation

1. Effect on the operation cycle
When the N:N Network is used, the operation cycle in each PLC becomes longer by about 10% regardless of
the number of linked stations and adopted communication patterns.
2. Program for setting the N:N Network
1) Make sure to create a program for setting the N:N Network from step 0 using M8038 (drive contact).
Otherwise, the N:N Network is disabled.
2) Do not set M8038 to ON using a program or programming tool.
3) Set station numbers consecutively. If a station number that is used twice or more is skipped, link will not
be achieved normally.
4) Pay close attention when setting up the N:N Network for the master station in a program using Structured
Ladder, FBD or ST programming in the FX
For details, refer to Section 7.2.
3. Program for reading link devices
Do not change the contents of link devices at other stations.
1) When a link error (data transfer sequence error) occurs, the link device information is held in the status
just before occurrence of the link error.
Create a fail-safe program which does not cause abnormality even if a link error occurs.
4. Cautions on using FX
1) Link pattern when FX
When FX
0N
setting).
If any other pattern is set, data transfer error occurs in all FX
the link time becomes longer.
2) When user devices are occupied as system devices
In FX /FX
0N
Network, and cannot be handled as general devices any more. Do not set these devices to ON or OFF
using a user program, display unit or programming tool.
If these devices are set to ON or OFF, the N:N Network may malfunction.
5. Cautions on using FX
1) Only ch 1 or ch 2 can be set in the N:N Network.
2) Do not use the N:N Network and parallel link at the same time.
(For example, it is not allowed to use ch1 for the N:N Network and use ch2 for parallel link.)
6. Link device update timing
Link device update in N:N network is executed in the interrupt processing.
Because the interrupt processing is generated asynchronously from operations of the sequence program, it
may be performed during ladder operation.
B-40
/FX PLCs
0N 1S
/FX PLCs are used or included
0N 1S
/FX PLCs are included in the system, make sure to set pattern 0 in D8178 (refresh range
1S
PLCs, M503 to M511 and D201 to D255 are handled as devices dedicated to the N:N
1S
/FX /FX
3G 3GC 3U
, FX , FX , FX
1S 1N 1NC 2N
0N
/FX PLCs
3UC
7.4 Cautions on Program Creation
or FX PLC.
2NC
/FX PLCs included in the system, and
1S
7 Creating Programs