PIC18F2331/2431/4331/4431
Continuous Loop mode allows the defined sequence to
21.1 Configuring the A/D Converter
be executed in a continuous loop when ACONV = 1. In
this mode, either the user can trigger the start of
conversion by setting the GO/DONE bit, or one of the
A/D triggers can start the conversion. The interrupt flag,
ADIF, is set based on the configuration of the bits,
ADRS<1:0> (ADCON3<7:6>). In Simultaneous modes,
STNM1 and STNM2 acquisition time must be config-
ured to ensure proper conversion of the analog input
signals.
The A/D Converter has two types of conversions, two
modes of operation and eight different Sequencing
modes. These features are controlled by the ACONV
bit (ADCON0<5>), ACSCH bit (ADCON0<4>) and
ACMOD<1:0> bits (ADCON0<3:2>). In addition, the
A/D channels are divided into four groups as defined
in the ADCHS register. Table 21-1 shows the
sequence configurations as controlled by the ACSCH
and ACMOD<1:0> bits.
21.1.2
CONVERSION MODE
21.1.1
CONVERSION TYPE
The ACSCH bit (ADCON0<4>) controls how many
channels are used in the configured sequence. When
clear, the A/D is configured for single channel conver-
sion and will convert the group selected by the
ACMOD<1:0> bits and the channel selected by the
GxSEL<1:0> bits (ADCHS register). When ACSCH = 1,
the A/D is configured for multiple channel conversion
and the sequence is defined by ACMOD<1:0>.
Two types of conversions exist in the high-speed 10-bit
A/D Converter module that are selected using the
ACONV bit. Single-Shot mode allows a single conversion
or sequence to be enabled when ACONV = 0. At the end
of the sequence, the GO/DONE bit will be automatically
cleared and the interrupt flag, ADIF, will be set. When
using Single-Shot mode and configured for
Simultaneous mode, STNM2, acquisition time must be
used to ensure proper conversion of the analog input
signals.
TABLE 21-1: AUTO-CONVERSION SEQUENCE CONFIGURATIONS
Mode
ACSCH ACMOD<1:0>
Description
Multi-Channel Sequential Mode 1
(SEQM1)
1
1
1
1
00
01
10
11
Groups A and B are sampled and converted
sequentially.
Multi-Channel Sequential Mode 2
(SEQM2)
Groups A, B, C and D are sampled and converted
sequentially.
Multi-Channel Simultaneous Mode 1
(STNM1)
Groups A and B are sampled simultaneously and
converted sequentially.
Multi-Channel Simultaneous Mode 2
(STNM2)
Groups A and B are sampled simultaneously, then
converted sequentially. Then, Group C and D are
sampled simultaneously, then converted
sequentially.
Single Channel Mode 1 (SCM1)
Single Channel Mode 2 (SCM2)
Single Channel Mode 3 (SCM3)
Single Channel Mode 4 (SCM4)
0
0
0
0
00
01
10
11
Group A is sampled and converted.
Group B is sampled and converted.
Group C is sampled and converted.
Group D is sampled and converted.
2010 Microchip Technology Inc.
DS39616D-page 247
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