ISD94100 Series Technical Reference Manual
Sep 9, 2019
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6.11.5.4 Time and Calendar counter
RTC_TIME and RTC_CAL are used to load the real time and calendar. RTC_TALM and
RTC_CALM are used for setup alarm time and calendar.
6.11.5.5 12/24 hour Time Scale Selection
The 12/24 hour time scale selection depends on 24HEN (RTC_CLKFMT[0]).
When RTC runs as 12-hour time scale mode, RTC_TIME[21] (the high bit of TENHR[1:0]) means
AM/PM indication, if RTC_TIME[21] is 1, it indicates PM time message and RTC_TIME[21] is 0
indicates AM time message. Table 6.11.5-2 shows RTC_TIME mapping table of 12/24 hour time
scale selection.
Note: The Hour Value Write Into RTC_TIME[21:16], Messages Are Expressed In BCD Format.
24-Hour Time Scale
(24HEN = 1)
12-Hour Time Scale (PM Time + 20)
(24HEN = 0) (PM Time + 20)
0x00 (AM12)
0x12 (PM12)
0x12 (AM12)
0x32 (PM12)
0x01 (AM01)
0x13 (PM01)
0x01 (AM01)
0x21 (PM01)
0x02 (AM02)
0x14 (PM02)
0x02 (AM02)
0x22 (PM02)
0x03 (AM03)
0x15 (PM03)
0x03 (AM03)
0x23 (PM03)
0x04 (AM04)
0x16 (PM04)
0x04 (AM04)
0x24 (PM04)
0x05 (AM05)
0x17 (PM05)
0x05 (AM05)
0x25 (PM05)
0x06 (AM06)
0x18 (PM06)
0x06 (AM06)
0x26 (PM06)
0x07 (AM07)
0x19 (PM07)
0x07 (AM07)
0x27 (PM07)
0x08 (AM08)
0x20 (PM08)
0x08 (AM08)
0x28 (PM08)
0x09 (AM09)
0x21 (PM09)
0x09 (AM09)
0x29 (PM09)
0x10 (AM10)
0x22 (PM10)
0x10 (AM10)
0x30 (PM10)
0x11 (AM11)
0x23 (PM11)
0x11 (AM11)
0x31 (PM11)
Table 6.11.5-2 12/24 hour Time Scale Selection
6.11.5.6 Day of the Week Counter
The RTC controller provides day of week in WEEKDAY bits (RTC_WEEKDAY[2:0]). The value is
defined from 0 to 6 to represent Sunday to Saturday respectively.
6.11.5.7 Periodic Time Tick Interrupt
The periodic time tick interrupt has 8 period interval options 1/128, 1/64, 1/32, 1/16, 1/8, 1/4, 1/2
and 1 second that are selected by TICK bits (RTC_TICK[2:0]). When periodic time tick interrupt is
enabled by setting TICKIEN (RTC_INTEN[1]) to 1, the periodic time tick interrupt is requested
periodically in the period selected by RTC_TICK[2:0] settings.
6.11.5.8 Alarm Interrupt
When the real time and calendar message in RTC_TIME and RTC_CAL registers are equal to
alarm time and calendar values in RTC_TALM and RTC_CALM registers, the RTC alarm interrupt
flag ALMIF (RTC_INTSTS[0]) is set to 1 and the RTC alarm interrupt signal assert if the alarm
interrupt enable ALMIEN (RTC_INTEN[0]) is enabled.