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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
552 of 808
NXP Semiconductors
UM10360
Chapter 29: LPC17xx Analog-to-Digital Converter (ADC)
5.2 A/D Global Data Register (AD0GDR - 0x4003 4004)
The A/D Global Data Register holds the result of the most recent A/D conversion that has
completed, and also includes copies of the status flags that go with that conversion.
Results of ADC conversion can be read in one of two ways. One is to use the A/D Global
Data Register to read all data from the ADC. Another is to use the
A/D Channel Data
Registers
. It is important to use one method consistently because the DONE and
OVERRUN flags can otherwise get out of synch between the AD0GDR and the
A/D
Channel Data Register
s, potentially causing erroneous interrupts or DMA activity.
26:24
START
When the BURST bit is 0, these bits control whether and when an A/D conversion is
started:
0
000
No start (this value should be used when clearing PDN to 0).
001
Start conversion now.
010
Start conversion when the edge selected by bit 27 occurs on the P2.10 / EINT0 / NMI pin.
011
Start conversion when the edge selected by bit 27 occurs on the P1.27 / CLKOUT /
USB_OVRCRn / CAP0.1 pin.
100
Start conversion when the edge selected by bit 27 occurs on MAT0.1. Note that this does
not require that the MAT0.1 function appear on a device pin.
101
Start conversion when the edge selected by bit 27 occurs on MAT0.3. Note that it is not
possible to cause the MAT0.3 function to appear on a device pin.
110
Start conversion when the edge selected by bit 27 occurs on MAT1.0. Note that this does
not require that the MAT1.0 function appear on a device pin.
111
Start conversion when the edge selected by bit 27 occurs on MAT1.1. Note that this does
not require that the MAT1.1 function appear on a device pin.
27
EDGE
This bit is significant only when the START field contains 010-111. In these cases:
0
1
Start conversion on a falling edge on the selected CAP/MAT signal.
0
Start conversion on a rising edge on the selected CAP/MAT signal.
31:28
-
Reserved, user software should not write ones to reserved bits. The value read from a
reserved bit is not defined.
NA
Table 513: A/D Control Register (AD0CR - address 0x4003 4000) bit description
Bit
Symbol Value
Description
Reset
value
Table 514: A/D Global Data Register (AD0GDR - address 0x4003 4004) bit description
Bit
Symbol
Description
Reset
value
3:0
-
Reserved, user software should not write ones to reserved bits. The value read from
a reserved bit is not defined.
NA
15:4
RESULT
When DONE is 1, this field contains a binary fraction representing the voltage on
the ADn.m pin selected by the SEL field, divided by the voltage on the V
DDA
pin
(V/V
REF
). Zero in the field indicates that the voltage on the AD0.n pin was less than,
equal to, or close to that on V
SSA
, while 0x3FF indicates that the voltage on AD0.n
was close to, equal to, or greater than that on V
REF
.
NA
23:16
-
Reserved, user software should not write ones to reserved bits. The value read from
a reserved bit is not defined.
NA
26:24
CHN
These bits contain the channel from which the RESULT bits were converted (e.g.
000 identifies channel 0, 001 channel 1...).
NA