PIC18F1220_07 Datasheet, PDF (157/308 Pages) Microchip Technology – 18/20/28-Pin High-Performance, Enhanced Flash Microcontrollers with 10-bit A/D and nanoWatt Technology

PIC18F1220/1320
17.0 10-BIT ANALOG-TO-DIGITAL
CONVERTER (A/D) MODULE
The Analog-to-Digital (A/D) converter module has
seven inputs for the PIC18F1220/1320 devices. This
module allows conversion of an analog input signal to
a corresponding 10-bit digital number.
A new feature for the A/D converter is the addition of
programmable acquisition time. This feature allows the
user to select a new channel for conversion and to set
the GO/DONE bit immediately. When the GO/DONE bit
is set, the selected channel is sampled for the pro-
grammed acquisition time before a conversion is actu-
ally started. This removes the firmware overhead that
may have been required to allow for an acquisition
(sampling) period (see Register 17-3 and Section 17.3
“Selecting and Configuring Automatic Acquisition
Time”).
The module has five registers:
• A/D Result High Register (ADRESH)
• A/D Result Low Register (ADRESL)
• A/D Control Register 0 (ADCON0)
• A/D Control Register 1 (ADCON1)
• A/D Control Register 2 (ADCON2)
The ADCON0 register, shown in Register 17-1,
controls the operation of the A/D module. The
ADCON1 register, shown in Register 17-2, configures
the functions of the port pins. The ADCON2 register,
shown in Register 17-3, configures the A/D clock
source, programmed acquisition time and justification.
REGISTER 17-1:
ADCON0: A/D CONTROL REGISTER 0
R/W-0 R/W-0
U-0
R/W-0
VCFG1 VCFG0
—
CHS2
bit 7
R/W-0
CHS1
R/W-0
CHS0
R/W-0
GO/DONE
R/W-0
ADON
bit 0
bit 7-6 VCFG<1:0>: Voltage Reference Configuration bits
A/D VREF+
00
AVDD
01 External VREF+
10
AVDD
11 External VREF+
A/D VREF-
AVSS
AVSS
External VREF-
External VREF-
bit 5
bit 4-2
bit 1
bit 0
Unimplemented: Read as ‘0’
CHS2:CHS0: Analog Channel Select bits
000 = Channel 0 (AN0)
001 = Channel 1 (AN1)
010 = Channel 2 (AN2)
011 = Channel 3 (AN3)
100 = Channel 4 (AN4)
101 = Channel 5 (AN5)
110 = Channel 6 (AN6)
111 = Unimplemented⁽¹⁾
GO/DONE: A/D Conversion Status bit
When ADON = 1:
1 = A/D conversion in progress
0 = A/D Idle
ADON: A/D On bit
1 = A/D converter module is enabled
0 = A/D converter module is disabled
Note 1: Performing a conversion on unimplemented channels returns full-scale results.
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared x = Bit is unknown
© 2007 Microchip Technology Inc.
DS39605F-page 155