UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
248 of 362
NXP Semiconductors
UM10208
Chapter 18: LPC2800 ADC
4.1 A/D Control Register (ADCCON - 0x8000 2420)
4.2 A/D Select Register (ADCSEL-0x8000 2424)
Table 277: A/D Control Register (ADCCON - 0x8000 2420)
Bit
Symbol
Description
Reset
value
0
SELVREF
Always write a 1 to this bit.
0
1
ADCENAB When this bit is 0, as it is after a Reset, power consumption is
minimized and A/D conversions cannot be done. Write a 1 to this bit to
enable the digital portion of the ADC, right after writing a 0 to the
ADCPD register to power up the analog portion of the ADC. Write a 0 to
this bit to disable the digital portion of the ADC, just before writing a 1 to
the ADCPD register to power down the analog portion of the ADC.
0
2
CSCAN
When this bit is 0, writing a 1 to the START bit makes the ADC convert
all of the analog inputs selected in the ADCSEL register, and then stop.
If this bit is 1, the ADC operates similarly, but continues converting the
selected input(s) again.
0
3
ADCSTRT Write a 1 to this bit to start conversion, then immediately write a 0 to this
bit, with the same values of ENABLE and CSCAN.
4
ADCBUSY This read-only bit is 1 when an ADC conversion is in progress. It is
cleared when the CSCAN bit is 0 and the ADC completes conversion of
the input(s) selected by ADCSEL. To terminate continuous conversion,
first write 0 to CSCAN, then wait for this bit to be 0. Power-down mode
is not entered until this bit is 0.
0
31:5 -
Reserved, user software should not write ones to reserved bits. The
value read from a reserved bit is not defined.
-
Table 278: A/D Select Register (ADCSEL-0x8000 2424)
Bit
Symbol Description
Reset
value
3:0
SEL0
If these bits are 0000, as they are after a reset, no conversion is done for
the AIN0 pad. 0010-1010 in this field selects AIN0 for conversion to the
number of result bits defined by this value. Other values are reserved
and should not be written.
0
7:4
SEL1
As described for SEL0, but for the AIN1 pad.
0
11:8
SEL2
As described for SEL0, but for the AIN2 pad.
0
15:12 SEL3
As described for SEL0, but for the AIN3 pad.
0
19:16 SEL4
As described for SEL0, but for the AIN4 pad.
0
23:20 SEL5
As described for SEL0, but for the DCDC_Vbat pad.
0
31:24 -
Reserved, user software should not write ones to reserved bits. The
value read from a reserved bit is not defined.
-