UM11029
All information provided in this document is subject to legal disclaimers.
© NXP Semiconductors N.V. 2017. All rights reserved.
User manual
Rev. 1.0 — 16 June 2017
449 of 515
NXP Semiconductors
UM11029
Chapter 26: LPC84x 12-bit Analog-to-Digital Converter (ADC)
26.6.3 A/D Conversion Sequence B 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 B sequence, as well bits to allow
software to initiate that conversion sequence.
To avoid conversions on spurious triggers, only change the trigger configuration when the
conversion sequence is disabled. A conversion can be triggered by software or hardware
in the conversion sequence, but if conversions are triggered by software only, spurious
hardware triggers must be prevented. See
Section 26.3.1 “Perform a single ADC
conversion using a software trigger”
.
Remark:
Set the BURST and SEQU_ENA bits at the same time.
31
SEQA_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 A is disabled. Sequence A triggers are ignored. If this
bit is cleared while sequence A 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 A is enabled.
Table 444. A/D Conversion Sequence A Control Register (SEQA_CTRL, address 0x4001 C008) bit description
Bit
Symbol
Value
Description
Reset
value
Table 445. A/D Conversion Sequence A Control Register (SEQA_CTRL, address 0x4001 C008) bit description
Bit
Symbol
Value
Description
Reset
value
11:0
CHANNELS
Selects which one or more of the twelve 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, A/D conversions will be performed
on each enabled channel, in sequence, beginning with the
lowest-ordered channel.
Remark:
This field can ONLY be changed while the SEQB_ENA bit
(bit 31) is LOW. It is permissible to change this field and set bit 31 in
the same write.
0x00
14:12
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.
Remark:
In order to avoid generating a spurious trigger, it is
recommended writing to this field only when the SEQA_ENA bit (bit
31) is low. It is safe to change this field and set bit 31 in the same
write.
0x0
17:15
-
Reserved.
-