11.3.1.1 Normal Mode
The main counter can receive a tick based on different tappings from the pre-counter, allowing the ticks to be power of 2 divisions of the
LFCLK
RTCC
. For more accurate configuration of the tick frequency, RTCC_CC0_CCV[14:0] can be used as a top value for
RTCC_PRECNT. When reaching the top value, the main counter receives a tick, and the pre-counter wraps around.
summarizes the resolutions available when using a 32768 Hz oscillator as
source for LFCLK
RTCC
.
Table 11.1. RTCC Resolution vs Overflow, F
LFCLK
= 32768 Hz
RTCC_CTRL_CNTTICK
RTCC_CTRL_CNTPRESC
Main counter period, T
CNT
Overflow
CCV0MATCH
Don't care
(RTCC_C 1)/F
LFCLK
s
2
32
*T
CNT
seconds
PRESC
DIV1
30.5 µs
36.4 hours
DIV2
61 µs
72.8 hours
DIV4
122 µs
145.6 hours
DIV8
244 µs
12 days
DIV16
488 µs
24 days
DIV32
977 µs
48 days
DIV64
1.95 ms
97 days
DIV128
3.91 ms
194 days
DIV256
7.81 ms
388 days
DIV512
15.6 ms
776 days
DIV1024
31.25 ms
4.2 years
DIV2048
62.5 ms
8.5 years
DIV4096
0.125 s
17 years
DIV8192
0.25 s
34 years
DIV16384
0.5 s
68 years
DIV32768
1 s
136 years
By default, the counter will keep counting until it reaches the top value, 0xFFFFFFFF, before it wraps around and continues counting
from zero. By setting CCV1TOP in RTCC_CTRL, a Capture/Compare channel 1 compare match will result in the main counter wrap-
ping to 0. The timer will then wrap around on a channel 1 compare match (RTCC_CNT = RTCC_CC1_CCV). If using the CCV1TOP
setting, make sure to set this bit prior to or at the same time the RTCC is enabled. Setting CCV1TOP after enabling the RTCC
(RTCC_CTRL_MODE != DISABLED) may cause unintended operation (e.g. if RTCC_CNT > RTCC_CC1_CCV, RTCC_CNT will wrap
when reaching 0xFFFFFFFF rather than RTCC_CC1_CCV).
EFM32JG1 Reference Manual
RTCC - Real Time Counter and Calendar
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