RTC_SS
20.3.5.14 RTC_CTRL_REG Register (offset = 40h) [reset = 0h]
RTC_CTRL_REG is shown in
and described in
.
The RTC_CTRL_REG contains the controls to enable/disable the RTC, set the 12/24 hour time mode, to
enable the 30 second rounding feature, and to STOP/START the RTC. The SET_32_COUNTER bit must
only be used when the RTC is frozen. The RTC_DISABLE bit must only be used to completely disable the
RTC function. When this bit is set, the 32 kHz clock is gated and the RTC is frozen. From this point,
resetting this bit to zero can lead to unexpected behavior. This bit should only be used if the RTC function
is unwanted in the application, in order to save power. MODE_12_24: It is possible to switch between the
two modes at any time without disturbing the RTC. Read or write is always performed with the current
mode. Auto compensation is enabled by the AUTO_COMP bit. If the COMP_REG value is positive,
compensation occurs after the second change event. COMP_REG cycles are removed from the next
second. If the COMP_REG value is negative, compensation occurs before the second change event.
COMP_REG cycles are added to the current second. This enables it to compensate with one 32-kHz
period accuracy each hour. The ROUND_30S bit is a toggle bit; the ARM can only write 1 and the RTC
clears it. If the ARM sets the ROUND_30S bit and then reads it, the ARM reads 1 until the round-to-the-
closest-minute is performed at the next second. The ARM can stop the RTC by clearing the STOP_RTC
bit (owing to internal resynchronization, the RUN bit of the status register (STATUS_REG) must be
checked to ensure that the RTC is frozen), then update TC values, and re-start the RTC by resetting the
STOP_RTC bit.
Figure 20-74. RTC_CTRL_REG Register
31
30
29
28
27
26
25
24
Reserved
R-0h
23
22
21
20
19
18
17
16
Reserved
R-0h
15
14
13
12
11
10
9
8
Reserved
R-0h
7
6
5
4
3
2
1
0
Reserved
RTC_DISABLE
SET_32_COUNTER
TEST_MODE
MODE_12_24
AUTO_COMP
ROUND_30S
STOP_RTC
R-0h
R/W-0h
R/W-0h
R/W-0h
R/W-0h
R/W-0h
R/W-0h
R/W-0h
LEGEND: R/W = Read/Write; R = Read only; W1toCl = Write 1 to clear bit; -n = value after reset
Table 20-77. RTC_CTRL_REG Register Field Descriptions
Bit
Field
Type
Reset
Description
31-7
Reserved
R
0h
6
RTC_DISABLE
R/W
0h
Disable RTC module and gate
32-kHz reference clock.
0x0 = RTC enable
0x1 = RTC disable (no 32 kHz clock)
5
SET_32_COUNTER
R/W
0h
Set the
32-kHz counter with the value stored in the compensation registers
when the SET_32_COUNTER bit is set.
0x0 = No action.
0x1 = Set the 32Khz counter with compensation registers value
4
TEST_MODE
R/W
0h
Test mode.
0x0 = Functional mode
0x1 = Test mode (Auto compensation is enabled when the 32Khz
counter reaches its end)
3647
SPRUH73H – October 2011 – Revised April 2013
Timers
Copyright © 2011–2013, Texas Instruments Incorporated