Datasheet

 1997 Microchip Technology Inc. DS30272A-page 39
PIC16C71X
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 7-4.
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 7.1.
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)
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 T
AD. A minimum wait of 2TAD is
required before next acquisition starts.
FIGURE 7-4: A/D BLOCK DIAGRAM
(Input voltage)
VIN
VREF
(Reference
voltage)
V
DD
PCFG1:PCFG0
CHS1:CHS0
00 or
10 or
11
01
RA3/AN3/V
REF
RA0/AN0
RA2/AN2
RA1/AN1
11
10
01
00
A/D
Converter