Maxim Integrated MAX32665 - RTC Calibration; Table 18-3. MAX32665-MAX32668 RTC Square Wave Output Configuration

MAX32665-MAX32668 User Guide
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compensated are used during the RTC frequency calibration procedure because they incorporate the frequency
adjustments provided by the digital trim function.
Table 18-3. MAX32665―MAX32668 RTC Square Wave Output Configuration
Function
Option
Control Field
Output Pin*
P0.19: SQWOUT
MCR_OUTEN.sqwout0en = 1
P0.27: SQWOUT
MCR_OUTEN.sqwout1en = 1
Frequency Select
1Hz (Compensated)
RTC_OSCCTRL.freq_sel = 0b00
512Hz (Compensated)
RTC_OSCCTRL.freq_sel = 0b01
4kHz
RTC_OSCCTRL.freq_sel = 0b10
32kHz
RTC_OSCCTRL.freq_sel = 0bxx
RTC_OSCCTRL.32k_out = 1
Output Enable
1Hz (Compensated)
RTC_CTRL.sqwout_en = 1
RTC_OSCCTRL.32k_out = 0
512Hz (Compensated)
RTC_CTRL.sqwout_en = 1
RTC_OSCCTRL.32k_out = 0
4kHz
RTC_CTRL.sqwout_en = 1
RTC_OSCCTRL.32k_out = 0
32kHz
RTC_OSCCTRL.32k_out = 1
*Note: The square wave output can be enabled on more than one pin if desired.
Use the following procedure to generate the square wave:
Software configures the fields shown in Table 18-3. to select the desired frequency.
If more than one output pin is available, software configures the fields shown in Table 18-3. MAX32665―MAX32668 RTC
Square Wave Output Configuration to select the output pin.
Software configures the fields shown in Table 18-3. to enable the square wave output.
18.5 RTC Calibration
A digital trim facility provides the ability to compensate for RTC inaccuracies of up to ± 127ppm when compared against an
external reference clock. The trimming function utilizes an independent, dedicated timer which increments the sub-second
register based on a user-supplied, 2’s compliment value in the RTC_TRIM register as shown in Figure 18-4. Internal
Implementation of Digital Trim, 4kHz.