UM10850
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User manual
Rev. 2.4 — 13 September 2016
368 of 464
NXP Semiconductors
UM10850
Chapter 25: LPC5410x 12-bit ADC controller (ADC0)
25.6.2 ADC Conversion Sequence A Control Register
There are two independent conversion sequences that can be configured, each consisting
of a set of conversions on one or more channels. This control register specifies the
channel selection and trigger conditions for the A sequence and contains bits to allow
software to initiate that conversion sequence.
Remark:
Set the BURST and SEQU_ENA bits at the same time.
Table 417: ADC Conversion Sequence A Control Register (SEQA_CTRL, address offset 0x08) bit description
Bit
Symbol
Value Description
Reset
value
11:0
CHANNELS
Selects which one or more of the ADC channels will be sampled and converted
when this sequence is launched. A 1 in any bit of this field will cause the
corresponding channel to be included in the conversion sequence, where bit 0
corresponds to channel 0, bit 1 to channel 1 and so forth.
When this conversion sequence is triggered, either by a hardware trigger or via
software command, ADC conversions will be performed on each enabled channel,
in sequence, beginning with the lowest-ordered channel.
Remark:
This field can ONLY be changed while SEQA_ENA (bit 31) is LOW. It is
allowed to change this field and set bit 31 in the same write.
0x00
17:12 TRIGGER
Selects which of the available hardware trigger sources will cause this conversion
sequence to be initiated. Program the trigger input number in this field. See
Remark:
In order to avoid generating a spurious trigger, it is recommended writing
to this field only when SEQA_ENA (bit 31) is low. It is safe to change this field and
set bit 31 in the same write.
0x0
18
TRIGPOL
Select the polarity of the selected input trigger for this conversion sequence.
Remark:
In order to avoid generating a spurious trigger, it is recommended writing
to this field only when SEQA_ENA (bit 31) is low. It is safe to change this field and
set bit 31 in the same write.
0
0
Negative edge. A negative edge launches the conversion sequence on the
selected trigger input.
1
Positive edge. A positive edge launches the conversion sequence on the selected
trigger input.
19
SYNCBYPASS
Setting this bit allows the hardware trigger input to bypass synchronization flip-flop
stages and therefore shorten the time between the trigger input signal and the start
of a conversion. There are slightly different criteria for whether or not this bit can
be set depending on the clock operating mode:
Synchronous mode (the ASYNMODE in the CTRL register = 0): Synchronization
may be bypassed (this bit may be set) if the selected trigger source is already
synchronous with the main system clock (eg. coming from an on-chip,
system-clock-based timer). Whether this bit is set or not, a trigger pulse must be
maintained for at least one system clock period.
Asynchronous mode (the ASYNMODE in the CTRL register = 1): Synchronization
may be bypassed (this bit may be set) if it is certain that the duration of a trigger
input pulse will be at least one cycle of the ADC clock (regardless of whether the
trigger comes from and on-chip or off-chip source). If this bit is NOT set, the trigger
pulse must at least be maintained for one system clock period.
0
0
Enable trigger synchronization. The hardware trigger bypass is not enabled.
1
Bypass trigger synchronization. The hardware trigger bypass is enabled.
25:20 -
Reserved. Read value is undefined, only zero should be written.
N/A