OMAP-L137 Low-Power Applications Processor
SPRS563A–SEPTEMBER 2008–REVISED OCTOBER 2008
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6.35.1 Clock Source
The clock reference for the RTC is an external 32.768-kHz crystal or an external clock source of the same
frequency. The RTC also has a separate power supply that is isolated from the rest of the system. When
the CPU and other peripherals are without power, the RTC can remain powered to preserve the current
time and calendar information.
The source for the RTC reference clock may be provided by a crystal or by an external clock source. The
RTC has an internal oscillator buffer to support direct operation with a crystal. The crystal is connected
between pins RTC_XI and RTC_XO. RTC_XI is the input to the on-chip oscillator and RTC_XO is the
output from the oscillator back to the crystal.
An external 32.768-kHz clock source may be used instead of a crystal. In such a case, the clock source is
connected to RTC_XI, and RTC_XO is left unconnected.
If the RTC is not used, the RTC_XI pin should be held low and RTC_XO should be left unconnected.
Switch for Device
Core Power
+1.2V
CVDD
Real Time Clock
C2
RTC_CVDD
RTC_X1
XTAL
32.768
kHz
Real
Time
Clock
(RTC)
Module
RTC_X0
32K
OSC
C1
RTC_VSS
Isolated RTC
Power Domain
Figure 6-70. Clock Source
6.35.2 Registers
Table 6-108 lists the memory-mapped registers for the RTC. See the device-specific data manual for the
memory address of these registers.
Table 6-108. Real-Time Clock (RTC) Registers
BYTE ADDRESS
0x01C2 3000
0x01C2 3004
0x01C2 3008
0x01C2 300C
0x01C2 3010
0x01C2 3014
0x01C2 3018
0x01C2 3020
Acronym
SECOND
MINUTE
HOUR
Register Description
Seconds Register
Minutes Register
Hours Register
DAY
Day of the Month Register
Month Register
MONTH
YEAR
Year Register
DOTW
Day of the Week Register
Alarm Seconds Register
ALARMSECOND
214
Peripheral Information and Electrical Specifications
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