UM10237_2 © NXP B.V. 2008. All rights reserved.
User manual Rev. 02 — 19 December 2008 660 o f 792
NXP Semiconductors UM10237
Chapter 26: LPC24XX Real-Time Clock (RTC) and battery RAM
11. Battery RAM
The Battery RAM is a 2 kbyte static RAM residing on the APB bus. The address range is
0xE008 4000 to 0xE008 47FF.The SRAM can be accessed word-wise (32-bit) only.
The Battery RAM is powered from the VBAT pin along with the RTC, both of which exist
in a power domain that is isolated from the rest of the chip. This allows them to operate
while the main chip power has been removed.
12. RTC external 32 kHz oscillator component selection
The RTC external oscillator circuit is shown in Figure 26–136. Since the feedback
resistance is integrated on chip, only a crystal, the capacitances CX1 and CX2 need to be
connected externally to the microcontroller.
Table 583. Pres caler cases where the Integer Counter reload value is incremented
Fraction Counter PREFRAC Bit
14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
--- ---- ---- ---1
1--------------
--- ---- ---- --10
-1-------------
--- ---- ---- -100
--1------------
--- ---- ---- 1000
---1-----------
--- ---- ---1 0000
----1----------
--- ---- --10 0000
-----1---------
--- ---- -100 0000
------1--------
--- ---- 1000 0000
-------1-------
--- ---1 0000 0000
--------1------
--- --10 0000 0000
---------1-----
--- -100 0000 0000
----------1----
--- 1000 0000 0000
-----------1---
--1 0000 0000 0000
------------1--
-10 0000 0000 0000
-------------1-
100 0000 0000 0000
--------------1