NXP Semiconductors LPC1751, User Manual, Page: 534 / 808

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UM10360_0 © NXP B.V. 2009. All rights reserved.
User manual Rev. 00.06 — 5 June 2009 534 of 808
NXP Semiconductors
UM10360
Chapter 27: LPC17xx Real-Time Clock (RTC) and backup registers
5. Pin description
6. Register description
The RTC includes a number of registers. The address space is split into four sections by
functionality. The first eight addresses are the Miscellaneous Register Group
(
Section 27–6.2 ). The second set of eight locations are the Time Counter Group
( Section 27–6.4 ). The third set of eight locations contain the Alarm Register Group
( Section 27–6.7 ).
The Real Time Clock includes the register shown in Table 27–489 . Detailed descriptions
of the registers follow. In these descriptions, for most of the registers the Reset Value
column shows "NC", meaning that these registers are Not Changed by a Reset. Software
must initialize these registers between power-on and setting the RTC into operation.
Table 488. RTC pin description
Name Type Description
RTCX1 I Input to the RTC oscillator circuit.
RTCX2 O Output from the RTC oscillator circuit.
Remark: If the RTC is not used, the RTCX1/2 pins can be left
floating.
V
BAT
I RTC power supply: Typically connected to an external 3V battery.
If this pin is not powered, the RTC is still powered internally if
V
DD(REG)(3V3)
is present.
Table 489. Real-Time Clock register map
Name Size Description Access Reset
Value
[1]
Address
Miscellaneous registers
ILR 2 Interrupt Location Register R/W 0 0x4002 4000
CCR 3 Clock Control Register R/W NC 0x4002 4008
CIIR 8 Counter Increment Interrupt Register R/W 0 0x4002 400C
AMR 8 Alarm Mask Register R/W 0 0x4002 4010
RTC_AUX 1 RTC Auxiliary control register R/W 0x8 0x4002 405C
RTC_AUXEN 1 RTC Auxiliary Enable register R/W 0 0x4002 4058
Consolidated time registers
CTIME0 32 Consolidated Time Register 0 RO NC 0x4002 4014
CTIME1 32 Consolidated Time Register 1 RO NC 0x4002 4018
CTIME2 32 Consolidated Time Register 2 RO NC 0x4002 401C
Time counter registers
SEC 6 Seconds Counter R/W NC 0x4002 4020
MIN 6 Minutes Register R/W NC 0x4002 4024
HOUR 5 Hours Register R/W NC 0x4002 4028
DOM 5 Day of Month Register R/W NC 0x4002 402C
DOW 3 Day of Week Register R/W NC 0x4002 4030
DOY 9 Day of Year Register R/W NC 0x4002 4034