Access Units - Mitsubishi Electric MELSEC iQ-R Series User Manual

Access units

The following table shows the number of accessible device points (access units) in one process (one scanning) when
accessing the device memory in a CPU module.
The access units of a CPU module other than the following modules depend on the module type.
Access target device type (series)
RCPU Programmable controller CPU
Process CPU
Safety CPU
C Controller module
*1 Access from a device other than an Ethernet port of an OPC UA server module
*2 Access via an Ethernet port of an OPC UA server module
Data inconsistency
When the number of accessed device points is equal to the access unit or less, device values in a same sequence scan are
obtained and applied.
When the number of device points exceeds the access unit, device values may be obtained from multiple sequence scans
and applied, which may cause data inconsistency.
■When data inconsistency is a problem
Set the following when a sequence program and the data needs to be synchronized and data inconsistency is a problem.
• Set the number of device points accessed at the same time to the access unit or less.
Device reading
*1
118 points
*2
58 points
Device writing
*1
78 points
*2
38 points
2 SPECIFICATIONS
2.2 Access Specifications for a CPU Module
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