PIC16LF877A-I Datasheet, PDF (131/234 Pages) Microchip Technology – 28/40/44-Pin Enhanced Flash Microcontrollers

PIC16F87XA
The ADRESH:ADRESL registers contain the 10-bit
result of the A/D conversion. When the A/D conversion
is complete, the result is loaded into this A/D Result
register pair, the GO/DONE bit (ADCON0<2>) is cleared
and the A/D interrupt flag bit ADIF is set. The block
diagram of the A/D module is shown in Figure 11-1.
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 inputs.
To determine sample time, see Section 11.1 “A/D
Acquisition Requirements”. After this acquisition
time has elapsed, the A/D conversion can be started.
To do an A/D Conversion, follow these steps:
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 PEIE 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
(interrupts disabled); OR
• Waiting for the A/D interrupt
6. Read A/D Result register pair
(ADRESH:ADRESL), clear bit ADIF if required.
7. For the next conversion, go to step 1 or step 2
as required. The A/D conversion time per bit is
defined as TAD.
FIGURE 11-1:
A/D BLOCK DIAGRAM
A/D
Converter
VAIN
(Input Voltage)
VDD
VREF+
(Reference
Voltage)
PCFG3:PCFG0
VREF-
(Reference
Voltage)
VSS
PCFG3:PCFG0
Note 1: Not available on 28-pin devices.
CHS2:CHS0
111
110
101
100
011
010
001
000
RE2/AN7⁽¹⁾
RE1/AN6⁽¹⁾
RE0/AN5⁽¹⁾
RA5/AN4
RA3/AN3/VREF+
RA2/AN2/VREF-
RA1/AN1
RA0/AN0
 2003 Microchip Technology Inc.
DS39582B-page 129