PIC16F7X7
The value in the ADRESH/ADRESL registers is not
modified for a Power-on Reset. The ADRESH/
ADRESL registers 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
conversion is started. The analog input channels must
have their corresponding TRIS bits selected as an
input. To determine acquisition time, see
After this acquisi-
tion time has elapsed, the A/D conversion can be
started. An acquisition time can be programmed to
occur between setting the GO/DONE bit and the actual
start of the conversion.
The following steps should be followed to do 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 acquisition time (ADCON2)
• 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
Wait the required acquisition time (if required).
Start conversion:
• Set GO/DONE bit (ADCON0 register)
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
Read A/D Result registers (ADRESH:ADRESL);
clear bit ADIF (if required).
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 2 T
AD
is
required before the next acquisition starts.
3.
4.
5.
6.
7.
FIGURE 12-1:
A/D BLOCK DIAGRAM
CHS<3:0>
1101
1100
1011
AN13
AN12
AN11
S
S
0011
AN3/V
REF
+
V
IN
(Input Voltage)
V
DD
A/D
Converter
V
REF
+
(Reference
Voltage)
VCFG<1:0>
0010
AN2/V
REF
-
0001
AN1
0000
AN0
V
REF
-
(Reference
Voltage)
V
SS
VCFG<1:0>
2004 Microchip Technology Inc.
DS30498C-page 155
MICROCHIP [ MICROCHIP TECHNOLOGY ]
