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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
1345 of 1441
NXP Semiconductors
UM10503
Chapter 48: 12-bit ADC (ADCHS)
The input channels are multiplexed to ADC input vin_pos. All six input channels share the
same vin_neg, which is generated internally when DCINNEG is set to 1 and output at pin
ADCHS_NEG. The nominal vin_neg level is 0.50 V. Hence vin_pos should be in the range
from 0.50 ± 0.4 V.
It is possible to deselect the internal vin_neg and supply vin_neg externally at pin
ADCHS_NEG by setting DCINNEG= 0.
The output format can be set to offset binary by setting TWOS to '0' (minimum code
0x000, maximum code 0xFFF) or to two's complement by setting TWOS to '1' (minimum
code 0x800, maximum code 0x7FF).
The ADC can be full switched off by setting both POWER_SWITCH and BGAP_SWITCH
to 0. In this case automatic wake up is not available (see
).
48.6.13 FIFO output register
These registers access the output FIFO that contains the 12-bit ADC conversion results.
All registers remap to the FIFO output. It is remapped 16 times to allow for DMA access
reading at 16 consecutive address locations.
SAMPLE is the conversion result value. CHAN_ID is the value of the sampled input (n:
input_n). When CHANNEL_ID_EN (see
) is set then CHAN_ID is always zero.
When PACKED_READ is set then two samples are packed into one 32-bit word. See
When an empty FIFO is read the output will be 0x8000 (or 0x80008000 for
PACKED_READ data).
Table 1135.Power control register (POWER_CONTROL, address 0x400F 0108) bit description
Bit
Symbol
Description
Reset
value
3:0
CRS
current setting for power versus speed programming
0x0
9 :4
DCINNEG
AC-DC coupling selection
0 = No dc bias
1 = DC bias on vin_neg side
0x0
15 : 10
DCINPOS
AC-DC coupling selection
0 = No dc bias
1 = DC bias on vin_pos side
0x0
16
TWOS
Output data format selection
0 = offset binary
1 = two’s complement
0x0
17
POWER_SWITCH
0 = ADC is powered down
1 = ADC is active
0x0
18
BGAP_SWITCH
0 = ADC band gap reference is powered down
1 = ADC band gap reference is active
0x0
31:19
-
Reserved
-