NXP Semiconductors
UM10699
User manual for SPI-bus RTC demoboard OM11059
UM10699
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© NXP B.V. 2013. All rights reserved.
User manual
Rev. 1 — 04 April 2013
6 of 12
Fig 5.
OM11059 schematics
4. Software set-up
4.1 Functionality
The RTC PCF85063BTL is controlled via standard SPI-bus interface. Common SPI
protocol applies.
Theoretically there is no lower speed limit, however the access of the RTC should be
performed within less than 1 second, otherwise time counter increments could be lost.
During access, the time registers of the RTC are frozen and after the read or write
sequence is completed, a seconds increment is executed if required.
The clock tracks the actual time from seconds to year. It must be initially set to the
correct time of the actual time zone. The days per month and leap year are corrected
automatically. Leap years are assumed whenever the year is dividable by 4.
The RTC can be programmed to generate an interrupt every 30 seconds or every
60 seconds.
At address byte 03h is a general purpose RAM byte to store temporary information.
4.2 System testing
There is a fast mode facility to test the functionality of the RTC; it can be activated by
setting the EXT_TEST bit in the Control_1 word.