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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
535 of 808
NXP Semiconductors
UM10360
Chapter 27: LPC17xx Real-Time Clock (RTC) and backup registers
[1]
Reset values apply only to a power-up of the RTC block, other types of reset have no effect on this block.
Since the RTC is powered whenever either of the V
DD(REG)(3V3)
, or V
BAT
supplies are present, power-up
reset occurs only when both supplies were absent and then one turns on. Most registers are not affected by
power-up of the RTC and must be initialized by software if the RTC is enabled. The Reset Value reflects the
data stored in used bits only. It does not include reserved bits content.
6.1 RTC interrupts
Interrupt generation is controlled through the Interrupt Location Register (ILR), Counter
Increment Interrupt Register (CIIR), the alarm registers, and the Alarm Mask Register
(AMR). Interrupts are generated only by the transition into the interrupt state. The ILR
separately enables CIIR and AMR interrupts. Each bit in CIIR corresponds to one of the
time counters. If CIIR is enabled for a particular counter, then every time the counter is
incremented an interrupt is generated. The alarm registers allow the user to specify a date
and time for an interrupt to be generated. The AMR provides a mechanism to mask alarm
compares. If all non-masked alarm registers match the value in their corresponding time
counter, then an interrupt is generated.
The RTC interrupt can bring the microcontroller out of Power-down mode when the RTC
is operating from its own oscillator on the RTCX1-2 pins. When the RTC interrupt is
enabled for wake-up and its selected event occurs, the oscillator wake-up cycle
associated with the XTAL1/2 pins is started. For details on the RTC based wake-up
process see
Section 4–8.8 “Wake-up from Reduced Power Modes” on page 54
and
Section 4–9 “Wake-up timer” on page 56
MONTH
4
Months Register
R/W
NC
0x4002 4038
YEAR
12
Years Register
R/W
NC
0x4002 403C
CALIBRATION
18
Calibration Value Register
NC
0x4002 4040
General purpose registers
GPREG0
32
General Purpose Register 0
R/W
NC
0x4002 4044
GPREG1
32
General Purpose Register 1
R/W
NC
0x4002 4048
GPREG2
32
General Purpose Register 2
R/W
NC
0x4002 404C
GPREG3
32
General Purpose Register 3
R/W
NC
0x4002 4050
GPREG4
32
General Purpose Register 4
R/W
NC
0x4002 4054
Alarm register group
ALSEC
6
Alarm value for Seconds
R/W
NC
0x4002 4060
ALMIN
6
Alarm value for Minutes
R/W
NC
0x4002 4064
ALHOUR
5
Alarm value for Hours
R/W
NC
0x4002 4068
ALDOM
5
Alarm value for Day of Month
R/W
NC
0x4002 406C
ALDOW
3
Alarm value for Day of Week
R/W
NC
0x4002 4070
ALDOY
9
Alarm value for Day of Year
R/W
NC
0x4002 4074
ALMON
4
Alarm value for Months
R/W
NC
0x4002 4078
ALYEAR
12
Alarm value for Year
R/W
NC
0x4002 407C
Table 489. Real-Time Clock register map
Name
Size
Description
Access Reset
Value
[1]
Address