
UM10800
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© NXP Semiconductors N.V. 2016. All rights reserved.
User manual
Rev. 1.2 — 5 October 2016
335 of 487
NXP Semiconductors
UM10800
Chapter 21: 12-bit Analog-to-Digital Converter (ADC)
21.6.4 A/D Global Data Register A and B
The A/D Global Data Registers contain the result of the most recent A/D conversion
completed under each conversion sequence.
Results of A/D conversions can be read in one of two ways. One is to use these A/D
Global Data Registers to read data from the ADC at the end of each A/D conversion.
Another is to read the individual A/D Channel Data Registers, typically after the entire
sequence has completed. It is recommended to use one method consistently for a given
conversion sequence.
The global registers are useful in conjunction with DMA operation - particularly when the
channels selected for conversion are not sequential (hence the addresses of the
individual result registers will not be sequential, making it difficult for the DMA engine to
address them). For interrupt-driven code it will more likely be advantageous to wait for an
entire sequence to complete and then retrieve the results from the individual channel
registers.
Remark:
The method to be employed for each sequence should be reflected in the
MODE bit in the corresponding ADSEQn_CTRL register since this will impact interrupt
and overrun flag generation.
31
SEQB_ENA
Sequence Enable. In order to avoid spuriously triggering the
sequence, care should be taken to only set the SEQA_ENA bit when
the selected trigger input is in its INACTIVE state (as defined by the
TRIGPOL bit). If this condition is not met, the sequence will be
triggered immediately upon being enabled.
0
0
Disabled. Sequence B is disabled. Sequence B triggers are ignored.
If this bit is cleared while sequence B is in progress, the sequence
will be halted at the end of the current conversion. After the
sequence is re-enabled, a new trigger will be required to restart the
sequence beginning with the next enabled channel.
1
Enabled. Sequence B is enabled.
Table 282. A/D Conversion Sequence A Control Register (SEQA_CTRL, address 0x4001 C008) bit description
Bit
Symbol
Value
Description
Reset
value