Considerations - Mitsubishi Electric MELSEC iQ-R C Series Programming Manual

Considerations

The following shows the considerations when using the MELSEC data link functions.
Considerations for programming
Open/close processing of a communication line (mdOpen/mdClose function)
Perform the open/close processing of communication line (the mdOpen/mdClose function) only once at the start of task (task
activation) and at the end of task (task completion) respectively in each user program. Opening/closing the line every
communication decreases the communication performance.
Execution after using the mdOpen function
At the first execution of the function after using the mdOpen function, it takes longer to execute the function since the CPU
module information needs to be acquired. The succeeding processing time can be shortened by performing dummy access at
the first time.
Access to other stations on the same task
Accessing 33 or more other stations simultaneously on the same task of C Controller module using a user program may
decrease the communication performance. To access other stations simultaneously on the same task, limit it to 32 or less
stations.
mdGetLabelInfo function call
The mdGetLabelInfo function does not need to be called each time to access a target CPU module.
Only if the error occurs (Error code: -81) when accessing by using the mdRandRLabelEx/mdRandWLabelEx function , call the
mdGetLabelInfo function again.
taskDelete execution
Do not execute the taskDelete in a task using the MELSEC data link function. Also, do not delete a task using the MELSEC
data link function with the taskDelete. Otherwise, the MELSEC data link function may not operate properly.
Accessing devices of the own station and of a CPU module on other stations
An interlock may be required to be provided depending on the link status of the own station and other stations.
Access to devices on the own station
Create a user program that provides an interlock to enable reading/writing data when the following conditions are satisfied to
access devices via each network module.
Module to be routed
CC-Link IE Controller Network module
CC-Link IE Field Network module
CC-Link IE TSN module
MELSECNET/H network module
CC-Link module
Even if the above conditions are not satisfied; however, read/write processing to the own station is completed normally.
Condition that requires interlock
When the following conditions are met:
• The bit of the own station data link error status (SB0049) is OFF (data linking).
• The bit corresponding to the communication target station that is stored in 'Data link status of each
station' (SW00B0 to SW00B7) is OFF (normal communication).
When the following conditions are met:
• The module status (SB20) is OFF (normal).
• The bit of the own station baton pass status (SB47) is OFF (normal).
• The bit of the own station data link status (SB49) is OFF (data linking).
When the following conditions are met:
• The module error (Xn0) is OFF (normal).
• 'Module READY' (XnF) is ON (activated).
• The bits of the own station data link status (Xn1) is ON (data linking).
1 COMMON ITEMS
1.3 MELSEC Data Link Functions
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