PIC16C72_13 Datasheet, PDF (55/128 Pages) Microchip Technology – 8-Bit CMOS Microcontrollers with A/D Converter

PIC16C72 Series
The ADRES register contains the result of the A/D con-
version. When the A/D conversion is complete, the
result is loaded into the ADRES register, the GO/DONE
bit (ADCON0<2>) is cleared, and A/D interrupt flag bit
ADIF is set. The block diagram of the A/D module is
shown in Figure 9-3.
The value that is in the ADRES register is not modified
for a Power-on Reset. The ADRES register will contain
unknown data after a Power-on Reset.
After the A/D module has been configured as desired,
the selected channel must be acquired before the con-
version is started. The analog input channels must
have their corresponding TRIS bits selected as an
input. To determine acquisition time, see Section 9.1.
After this acquisition time has elapsed the A/D conver-
sion can be started. The following steps should be fol-
lowed for doing an A/D conversion:
1. Configure the A/D module:
• Configure analog pins / voltage reference /
and digital I/O (ADCON1)
• Select A/D input channel (ADCON0)
• Select A/D conversion clock (ADCON0)
• Turn on A/D module (ADCON0)
FIGURE 9-3: A/D BLOCK DIAGRAM
2. Configure A/D interrupt (if desired):
• Clear ADIF bit
• Set ADIE bit
• Set GIE bit
3. Wait the required acquisition time.
4. Start conversion:
• Set GO/DONE bit (ADCON0)
5. Wait for A/D conversion to complete, by either:
• Polling for the GO/DONE bit to be cleared
OR
• Waiting for the A/D interrupt
6. Read A/D Result register (ADRES), clear bit
ADIF if required.
7. For next conversion, go to step 1 or step 2 as
required. The A/D conversion time per bit is
defined as TAD. A minimum wait of 2TAD is
required before next acquisition starts.
CHS2:CHS0
VAIN
(Input voltage)
100
RA5/AN4
011
RA3/AN3/VREF
A/D
Converter
010
RA2/AN2
001
RA1/AN1
VDD
000
RA0/AN0
VREF
000 or
010 or
100
(Reference
voltage)
001 or
011 or
101
PCFG2:PCFG0
 1998-2013 Microchip Technology Inc.
Preliminary
DS39016B-page 55