PIC18F2331_07 Datasheet, PDF (255/400 Pages) Microchip Technology – 28/40/44-Pin Enhanced Flash Microcontrollers with nanoWatt Technology, High Performance PWM and A/D

PIC18F2331/2431/4331/4431
20.1 Configuring the A/D Converter
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 20-1 shows the
sequence configurations as controlled by the ACSCH
and ACMOD<1:0> bits.
20.1.1 CONVERSION TYPE
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.
Continuous Loop mode allows the defined sequence to
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.
20.1.2 CONVERSION MODE
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>.
TABLE 20-1: AUTO-CONVERSION SEQUENCE CONFIGURATIONS
Mode
ACSCH ACMOD<1:0>
Description
Multi-Channel Sequential Mode 1
1
(SEQM1)
Multi-Channel Sequential Mode 2
1
(SEQM2)
Multi-Channel Simultaneous Mode 1
1
(STNM1)
Multi-Channel Simultaneous Mode 2
1
(STNM2)
Single Channel Mode 1 (SCM1)
0
Single Channel Mode 2 (SCM2)
0
Single Channel Mode 3 (SCM3)
0
Single Channel Mode 4 (SCM4)
0
00
Groups A and B are sampled and converted
sequentially.
01
Groups A, B, C and D are sampled and converted
sequentially.
10
Groups A and B are sampled simultaneously and
converted sequentially.
11
Groups A and B are sampled simultaneously, then
converted sequentially. Then, Group C and D are
sampled simultaneously, then converted
sequentially.
00
Group A is sampled and converted.
01
Group B is sampled and converted.
10
Group C is sampled and converted.
11
Group D is sampled and converted.
© 2007 Microchip Technology Inc.
Preliminary
DS39616C-page 253