PIC18F8493 Microchip Technology, PIC18F8493 Datasheet - Page 35

• Manufacturer Part Number: PIC18F8493
• Description: Flash Microcontrollers
• Manufacturer: Microchip Technology

The value in the ADRESH:ADRESL registers is
unknown following Power-on and Brown-out Resets and
is not affected by any other 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 Section 2.1
“A/D Acquisition Requirements”. 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 perform an A/D
conversion:
1.
2.
3.
4.
FIGURE 2-3:
© 2009 Microchip Technology Inc.
Configure the A/D module:
• Configure analog pins, voltage reference and
• Select A/D input channel (ADCON0)
• Select A/D acquisition time (ADCON2)
• Select A/D conversion clock (ADCON2)
• Turn on A/D module (ADCON0)
Configure A/D interrupt (if desired):
• Clear ADIF bit
• Set ADIE bit
• Set GIE bit
Wait the required acquisition time (if required).
Start conversion:
• Set GO/DONE bit (ADCON0<1>)
digital I/O (ADCON1)
Legend: C
V
AIN
Rs
ANALOG INPUT MODEL
V
I
R
SS
C
R
LEAKAGE
T
PIN
IC
HOLD
SS
ANx
C
5 pF
PIN
= Input Capacitance
= Threshold Voltage
= Leakage Current at the pin due to
= Interconnect Resistance
= Sampling Switch
= Sample/Hold Capacitance (from DAC)
= Sampling Switch Resistance
various junctions
V
PIC18F6393/6493/8393/8493
DD
V
V
T
T
= 0.6V
= 0.6V
I
±100 nA
5.
6.
7.
FIGURE 2-2:
LEAKAGE
R
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 the next conversion, go to step 1 or step 2,
as required. The A/D conversion time per bit is
defined as T
required before the next acquisition starts.
FFEh
FFFh
IC
003h
002h
001h
000h
≤ 1k
V
Sampling
SS
DD
Switch
AD
6V
5V
4V
3V
2V
R
. A minimum wait of 2 T
Analog Input Voltage
SS
A/D TRANSFER FUNCTION
Sampling Switch
1
V
C
SS
2
HOLD
3
= 25 pF
DS39896B-page 35
www.DataSheet4U.com
4
(kΩ)
AD
is