Mitsubishi Electric MELSEC Q Series User Manual page 164

(5) Multiple CPU clock synchronization function
The multiple CPU clock synchronization function allows clock data synchronization with CPU No.1 when the C
Controller module is set as CPU No.2, No.3, or No.4 in a multiple CPU system.
Clock data will be received from CPU No.1 at the following timing.
• When the multiple CPU system is powered on
• When the multiple CPU system status is changed from RESET or STOP to RUN
• At intervals of one second after startup of the multiple CPU system
• As clock data are set in seconds by the No.1 CPU module, clock data for other CPU modules may be different
from the No.1 CPU module's scan time by up to 1 second.
• The C Controller modules (Q12DCCPU-V, Q24DHCCPU-V, and Q24DHCCPU-VG) synchronize the clock data if
there is any discrepancy of 3 seconds or more between the clock data received from No.1 module and the clock
data in the C Controller module.
• Clock data of CPU No.1 must be set to the year 2000 or later.
The C Controller module supports only the year 2000 or later clock data.
(a) When using the time setting function (SNTP)
For No.2 through No.4 modules, the time synchronization with the No.1 CPU module has a priority, so time
synchronization by "Time setting function (SNTP)" will not be conducted.
(b) When using GOT time adjustment and time notification
The No.1 CPU module is the target when performing time adjustment and time notification by GOT connected
to the No.2 to No.4 C Controller modules.
Synchronize the clocks of No.2-4 modules with that of the No.1.
(6) Precautions
(a) Initial clock data setting
No clock data are set for the C Controller module prior to shipping.
Therefore, before using the C Controller module for the first time, be sure to set accurate clock time.
(b) Correcting clock data
Even if a part of clock data is to be corrected, all of clock data must be written to the C Controller module again.
(c) Changing clock data by a user program
When changing clock data by a user program, use the C Controller module dedicated function
(CCPU_SetRTC).
If any other clock data setting function is used, correct clock data will not be set in the C Controller module.
(d) Standard time
The C Controller module integral clock cannot use the local standard time and the global standard time
simultaneously.
Set the local standard time to set time to the integral clock.
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