UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
1162 of 1269
NXP Semiconductors
UM10503
Chapter 44: LPC43xx 10-bit ADC0/1
44.7 Operation
44.7.1 Hardware-triggered conversion
If the BURST bit in the ADCR is 0 and the START field contains any value between 0x2
and 0x6, the A/D converter will start a conversion when a transition occurs on a selected
pin or Timer signal. The choices include the two ADCTRIG external input pins, an output
from the motocon PWM, and two combined timer outputs (see
).
The result of a hard-ware triggered conversion is stored in the individual channel data
registers DR0 to DR7. The global data register does not yield valid readings of a
hardware-triggered conversion.
44.7.2 Interrupts
An interrupt is requested to the NVIC when the ADINT bit in the ADSTAT register is 1. The
ADINT bit is one when any of the DONE bits of the A/D channels which are enabled for
interrupts (via the ADINTEN register) are one. Software can use the Interrupt Enable bit in
the NVIC that corresponds to the ADC to control whether this results in an interrupt. The
result register of the A/D channel which is generating an interrupt must be read in order to
clear the corresponding DONE flag.
44.7.3 DMA control
A DMA transfer request is generated from the ADC interrupt request line. To generate a
DMA transfer the same conditions must be met as the conditions for generating an
interrupt. A pending DMA request is cleared after the DMA has read from the requesting
channel’s A/D data register (DR[7:0]). Reading from the global data register (GDR) does
not clear any pending DMA requests.
For DMA transfers, only burst requests are supported. The burst size can be set to one of
the predefined burst sizes in the DMA channel control register (see
). If the
number of ADC channels is not equal to one of the predefined DMA-supported burst sizes
(applicable DMA burst sizes are 1, 4, 8), set the burst size to one.
Table 1014.A/D Status register (STAT - address 0x400E 3030 (ADC0) and 0x400E 4030
(ADC1)) bit description
Bit
Symbol
Description
Reset
value
7:0
DONE
These bits mirror the DONE status flags that appear in the result
register for each A/D channel.
0
15:8
OVERUN
These bits mirror the OVERRRUN status flags that appear in the
result register for each A/D channel. Reading ADSTAT allows
checking the status of all A/D channels simultaneously.
0
16
ADINT
This bit is the A/D interrupt flag. It is one when any of the individual
A/D channel Done flags is asserted and enabled to contribute to the
A/D interrupt via the ADINTEN register.
0
31:17 -
Reserved. Always 0.
0