Datasheet

© 2007 Microchip Technology Inc. DS39629C-page 231
PIC18F6390/6490/8390/8490
18.0 10-BIT ANALOG-TO-DIGITAL
CONVERTER (A/D) MODULE
The Analog-to-Digital (A/D) converter module has
12 inputs for the PIC18F6X90/8X90 devices. This
module allows conversion of an analog input signal to
a corresponding 10-bit digital number.
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 18-1,
controls the operation of the A/D module. The
ADCON1 register, shown in Register 18-2, configures
the functions of the port pins. The ADCON2 register,
shown in Register 18-3, configures the A/D clock
source, programmed acquisition time and justification.
REGISTER 18-1: ADCON0: A/D CONTROL REGISTER 0
U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
— — CHS3 CHS2 CHS1 CHS0 GO/DONE ADON
bit 7 bit 0
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
bit 7-6 Unimplemented: Read as ‘0’
bit 5-2 CHS3:CHS0: Analog Channel Select bits
0000 = Channel 0 (AN0)
0001 = Channel 1 (AN1)
0010 = Channel 2 (AN2)
0011 = Channel 3 (AN3)
0100 = Channel 4 (AN4)
0101 = Channel 5 (AN5)
0110 = Channel 6 (AN6)
0111 = Channel 7 (AN7)
1000 = Channel 8 (AN8)
1001 = Channel 9 (AN9)
1010 = Channel 10 (AN10)
1011 = Channel 11 (AN11)
1100 = Unimplemented
(1)
1101 = Unimplemented
(1)
1110 = Unimplemented
(1)
1111 = Unimplemented
(1)
bit 1 GO/DONE: A/D Conversion Status bit
When ADON =
1:
1 = A/D conversion in progress
0 = A/D Idle
bit 0 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 will return a floating input measurement.