Security Function - Mitsubishi Electric MELSEC Q Series User Manual

(3) Refresh time check
The actual refresh time values (maximum, minimum and current values) while the C Controller system is running
can be checked by using Setting/monitoring tools for the C Controller module.
•
[Diagnostics]  [CCPU diagnostics]  <<CCPU diagnostics>>  "Refresh information"
(a) Refresh time
From "Refresh time" in "Refresh information," the actual measurement value for the total refresh time can be checked.
(Total refresh time = Link refresh time + Data refresh time)
Use the confirmed maximum refresh time value as a reference to set the refresh cycle.
(b) Link refresh time
From "Link refresh time" in "Refresh information," the actual measurement value for the total link refresh time
for all network modules controlled by the C Controller module can be checked.
(c) Data refresh time
From "Data refresh time" in "Refresh information," the actual measurement value for the data refresh time can
be checked.
If the user program processing performance is poor, i.e. higher downtime ratio relative to the user program operation time,
perform the following processing as necessary.
• Increase the refresh cycle setting value.
• Reduce the number of link refresh points to shorten the link refresh time. ( Page 249, Section 13.5.3)
• Review the user program task configuration, priority and processing, etc.
11.8

Security Function

This function limits operations to the C Controller module to protect data.
The Security function is one of the methods for preventing illegal access (such as program or data corruption) from an
external device. However, this function does not prevent illegal access completely. Incorporate measures other than this
function if the C Controller system's safety must be maintained against illegal access from an external device. Mitsubishi
Electric Corporation cannot be held responsible for any system problems that may occur from illegal access.
Examples of measures for illegal access are shown below.
• Install a firewall.
• Install a personal computer as a relay station, and control the relay of send/receive data with an application
program.
• Install an external device for which the access rights can be controlled as a relay station. (For details on the
external devices for which access rights can be controlled, consult the network provider or equipment dealer.)
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Q24DHC-V Q24DHC-VG Q24DHC-LS Q26DHC-LS Q12DC-V