PIC24EP256GU810-I Datasheet, PDF (451/622 Pages) Electronic Film Capacitors, Inc. – 16-Bit Microcontrollers and Digital Signal Controllers with High-Speed PWM, USB and Advanced Analog

dsPIC33EPXXX(GP/MC/MU)806/810/814 and PIC24EPXXX(GP/GU)810/814
26.1 Writing to the RTCC Timer
Note:
To allow the RTCC module to be clocked by
the secondary crystal oscillator, the Sec-
ondary Oscillator Enable (LPOSCEN) bit in
the Oscillator Control (OSCCON<1>) regis-
ter must be set. For further details, refer to
Section 7. “Oscillator” (DS70580) in the
“dsPIC33E/PIC24E Family Reference
Manual”.
The user application can configure the time and
calendar by writing the desired seconds, minutes,
hours, weekday, date, month and year to the RTCC
registers. Under normal operation, writes to the RTCC
Timer registers are not allowed. Attempted writes will
appear to execute normally, but the contents of the
registers will remain unchanged. To write to the RTCC
register, the RTCWREN bit (RCFGCAL<13>) must be
set. Setting the RTCWREN bit allows writes to the
RTCC registers. Conversely, clearing the RTCWREN
bit prevents writes.
To set the RTCWREN bit, the following procedure must
be executed. The RTCWREN bit can be cleared at any
time:
1. Write 0x55 to NVMKEY.
2. Write 0xAA to NVMKEY.
3. Set the RTCWREN bit using a single-cycle
instruction.
The RTCC module is enabled by setting the RTCEN bit
(RCFGCAL<15>). To set or clear the RTCEN bit, the
RTCWREN bit (RCFGCAL<13>) must be set.
If the entire clock (hours, minutes and seconds) needs
to be corrected, it is recommended that the RTCC
module should be disabled to avoid coincidental write
operation when the timer increments. Therefore, it
stops the clock from counting while writing to the RTCC
Timer register.
26.2 RTCC Resources
Many useful resources related to RTCC are provided
on the main product page of the Microchip web site for
the devices listed in this data sheet. This product page,
which can be accessed using this link, contains the
latest updates and additional information.
Note:
In the event you are not able to access the
product page using the link above, enter
this URL in your browser:
http://www.microchip.com/wwwproducts/
Devices.aspx?dDocName=en554310
26.2.1 KEY RESOURCES
• Section 29. “Real-Time Clock and Calendar
(RTCC)” (DS70584) in the “dsPIC33E/PIC24E
Family Reference Manual”
• Code Samples
• Application Notes
• Software Libraries
• Webinars
• All related “dsPIC33E/PIC24E Family Reference
Manual” Sections
• Development Tools
 2009-2012 Microchip Technology Inc.
DS70616G-page 451