Xycom XVME-113, User Manual

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Chapter 3 – Real Time Clock
3-8
3.4.7.1 RAM
7-4
These bits may be used as RAM or as flag bits at the user's discretion. These are readable/writable bits which retain their
state upon power down. These bits may only be used if the TEST bit has been set to '0'.
3.4.7.2 TEST
This bit is used to test the RTC at the factory and should always be set to '0' by the user's program. Failure to do so will
result in improper operation of the RTC.
3.4.7.3
ADJ (30-Second Adjust)
This bit is used to execute the 30-second adjustment feature of the RTC, which can be used to automatically synchronize
the RTC to another clock source. When a '1' is written to this bit, the Minutes Counter Register will be adjusted
according to the value in the Seconds Counter Register. If the Seconds Counter Register value is less than 30, the
Minutes Counter Register is unchanged. Otherwise, a carry will occur in the Minutes Counter Register. The 64 Hz
Counter Register and the Seconds Counter Register are both reset to 00h.
After being written to '1', the ADJ bit will remain set for 250 µs while the 30-second adjust operation takes place. The
bit will then be reset to '0' automatically.
3.4.7.4
RESET
This bit is used to reset the 64 Hz Counter Register to 00h to initialize the dividing circuit. This operation is typically
done with the counter stopped in order to set the RTC time and date before restarting the RTC.
After being written to '1', the RESET bit will remain set for 250 µs while the reset operation takes place. The bit will
then be reset to '0' automatically.
3.4.7.5 Start/Stop
This bit is used to start and stop the RTC. When a '0' is written to this bit, the RTC stops counting. When a '1' is written
to this bit, counting begins (or continues).