Mitsubishi Electric MELSEC iQ-R Series User Manual page 92

Precautions
This section describes the precautions on the device/label access service processing setting.
■Functions that may prolong the scan time
For the following functions, the scan time may become longer than the specified time during processing even when this
setting is applied.
• Online change
• Device/buffer memory batch monitor
• Data logging function
• File register write or read
*1 The scan time becomes longer when the size of data to write or read is large.
■When constant scan is set
The CPU module always processes one request during the END processing, and processes the remaining requests during
the wait time for the next constant scan. Set constant scan setting time considering the time required for the device/label
access service processing to execute.
■When "Execute END Processing between Programs" is enabled
When "Execute END Processing between Programs" is enabled, the device/label access service processing, such as device
access, is performed between program executions and during the END processing. Therefore, when monitoring and current
value change are performed in the situation where a device value is processed across programs, values of ongoing operation
may be read or written.
Also, when "Execute END Processing between Programs" is enabled, if monitoring and current value change are performed
for the file register where "Use File Register of Each Program" is enabled, unintended data may be obtained or written. In this
case, the value of the file register may not fall into the range depending on whether the file register is used for each program
and the size of the file register.
*1 Because the timing of monitoring or current value change (during execution of a program or the END processing) cannot be specified,
values of ongoing operation may be read or written.
*2 Because monitoring is performed between programs and the operation is executed during the END processing, a file register to be
registered and whose current value is to be changed cannot be specified.
8 RUNNING A PROGRAM
90
8.2 Scan Time
*1
*1
* 2