Mitsubishi Electric MELSEC iQ-R-R00CPU, User Manual

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4 CLOCK FUNCTION
4.3 Daylight Saving Time Function
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Daylight saving time function operation check
The daylight saving time function operation can be checked as follows.
Special relay
SM217 (Daylight saving time status flag) can be used to check whether the date lies inside or outside the daylight saving time
period. (
 Page 803 List of Special Relay Areas)
Event history
The history for the start and end of daylight saving time can be checked in the event history for the date set in "Setting to
Adjust Clock for Daylight Saving Time" (

Page 790 Event list)
Operation of other functions using clock data during daylight
saving time
Functions using CPU module clock data operate as follows during the daylight saving time period.
Precautions
This section describes precautions on the daylight saving time function.
• The clock data cannot be changed to data less than one hour from the starting time of the daylight saving time.
Furthermore, if the "Setting to Adjust Clock for Daylight Saving Time" for CPU No.1 in a multiple CPU system is enabled, it
will not be possible to change the clock data to data less than one hour from the starting time of the daylight saving time for
CPU modules for CPU Nos. 2 to 4.
• For the period less than one hour from the starting time or less than one hour until the ending time of daylight saving time,
the function that is triggered by time may not work or may work twice.
• When the "Setting to Adjust Clock for Daylight Saving Time" is enabled, functions operate based on date information after
adjustment for daylight saving time. For this reason, dates and times output by functions that uses clock data are reversed
((before adjustment)

(after adjustment)) and therefore the order (No.) in which events occur and the sorting order for the
date on which events occur may not match. Consequently, when checking output results in chronological order, sort not in
the order for the date on which events occur, but in the order (No.) in which events occur.
Ex.
Event history
Since the time goes back one hour at No.00005 where the daylight saving time ends, the dates and times on which events
occurred are reversed at the upper and lower side of the broken line ((time of new event history) < (time of old event history)).
Item Description
Clock data reading Reads clock data following adjustment for daylight saving time.
Clock data writing Writes as clock data following adjustment for daylight saving time.