UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
147 of 362
NXP Semiconductors
UM10208
Chapter 13: LPC2800 RTC
[1]
Registers in the RTC other than those that are part of the Prescaler are not affected by chip Reset. These
registers must be initialized by software if the RTC is enabled. Reset Value reflects the data stored in used
bits only. It does not include reserved bits content.
6.1 Miscellaneous register group
summarizes these registers. More detailed descriptions follow.
6.1.1 RTC Configuration Register (RTC_CFG - 0x8000 5024)
This register is located in the "System Configuration" address range, but it is described
here because it is dedicated to the RTC.
Note that because the PWR_UP bit resets to 0, software must always write a 1 to this bit
before it can access any of the other registers in the RTC.
6.1.2 Interrupt Location Register (ILR - 0x8000 2000)
The Interrupt Location Register is a 2 bit register that specifies which blocks are
generating an interrupt (see
). Writing a one to the appropriate bit clears the
corresponding interrupt. Writing a zero has no effect. This allows software to read this
register and write back the same value, to clear only the interrupt that is detected by the
read.
Table 152. Miscellaneous registers
Name
Size
Description
Access Address
RTC_CFG 1
Enables or disables software access to the RTC.
R/W
0x8000 5024
ILR
3
Interrupt Location. Reading this location indicates the
source of an interrupt. Writing a one to the
appropriate bit at this location clears the associated
interrupt.
R/W
0x8000 2000
CTC
15
Clock Tick Counter. Value from the clock divider.
RO
0x8000 2004
CCR
4
Clock Control Register. Controls the function of the
clock divider.
R/W
0x8000 2008
CIIR
8
Counter Increment Interrupt. Selects which counters
will generate an interrupt when they are incremented.
R/W
0x8000 200C
AMR
8
Alarm Mask Register. Controls which of the alarm
registers are masked.
R/W
0x8000 2010
CTIME0
32
Consolidated Time Register 0
RO
0x8000 2014
CTIME1
32
Consolidated Time Register 1
RO
0x8000 2018
CTIME2
32
Consolidated Time Register 2
RO
0x8000 201C
Table 153. RTC Configuration Register (RTC_CFG - 0x8000 5024)
Bit
Symbol
Description
Reset
value
0
PWR_UP When this bit is 1, software can read and write the RTC registers. When
it is 0, all bus interface inputs are gated. Besides the first element in the
ripple counter, and the optional alarm clock sampling flip flop, all loads
to the 32.768 kHz clock are gated to reduce power.
0
31:1
-
Reserved, user software should not write ones to reserved bits. The
value read from a reserved bit is not defined.
NA