UM10237_2 © NXP B.V. 2008. All rights reserved.
User manual Rev. 02 — 19 December 2008 649 o f 792
NXP Semiconductors UM10237
Chapter 26: LPC24XX Real-Time Clock (RTC) and battery RAM
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 26–6.2). The second set of eight locations are the Time Counter Group
(Section 26–6.4). The third set of eight locations contain the Alarm Register Group
(Section 26–7). The remaining registers control the Reference Clock Divider.
The Real Time Clock includes the register shown in Table26–566. 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 566. Summ ary of Real-Time Clock registers
Name Size Description Access Reset
Value[1] Address
ILR 2 Interrupt Location Register R/W NC 0xE002 4000
CTC 15 Clock Tick Counter RO NC 0xE002 4004
CCR 4 Clock Control Register R/W NC 0xE002 4008
CIIR 8 Counter Increment Interrupt Register R/W NC 0xE002 400C
AMR 8 Alarm Mask Register R/W NC 0xE002 4010
CTIME0 32 Consolidated Time Register 0 RO NC 0xE002 4014
CTIME1 32 Consolidated Time Register 1 RO NC 0xE002 4018
CTIME2 32 Consolidated Time Register 2 RO NC 0xE002 401C
SEC 6 Seconds Counter R/W NC 0xE002 4020
MIN 6 Minutes Register R/W NC 0xE002 4024
HOUR 5 Hours Register R/W NC 0xE002 4028
DOM 5 Day of Month Register R/W NC 0xE002 402C
DOW 3 Day of Week Register R/W NC 0xE002 4030
DOY 9 Day of Year Register R/W NC 0xE002 4034
MONTH 4 Months Register R/W NC 0xE002 4038
YEAR 12 Years Register R/W NC 0xE002 403C
CISS 8 Counter Increment select mask for
Sub-Second interrupt R/W NC 0xE002 4040
ALSEC 6 Alarm value for Seconds R/W NC 0xE002 4060
ALMIN 6 Alarm value for Minutes R/W NC 0xE002 4064
ALHOUR 5 Alarm value for Seconds R/W NC 0xE002 4068
ALDOM 5 Alarm value for Day of Month R/W NC 0xE002 406C
ALDOW 3 Alarm value for Day of Week R/W NC 0xE002 4070
ALDOY 9 Alarm value for Day of Year R/ W NC 0xE002 4074
ALMON 4 Alarm value for Months R/W NC 0xE002 4078
ALYEAR 12 Al arm value for Year R/W NC 0xE002 407C
PREINT 13 Prescaler value, integer portion R/W 0 0xE00240 80
PREFRAC 15 Prescaler value, fractional portion R/W 0 0xE0024084