PIC16F87XA
The A/D module has four registers. These registers are:
11.0 ANALOG-TO-DIGITAL
CONVERTER (A/D) MODULE
• A/D Result High Register (ADRESH)
• A/D Result Low Register (ADRESL)
• A/D Control Register0 (ADCON0)
• A/D Control Register1 (ADCON1)
The Analog-to-Digital (A/D) Converter module has five
inputs for the 28-pin devices and eight for the 40/44-pin
devices.
The ADCON0 register, shown in Register 11-1, con-
trols the operation of the A/D module. The ADCON1
register, shown in Register 11-2, configures the func-
tions of the port pins. The port pins can be configured
as analog inputs (RA3 can also be the voltage refer-
ence), or as digital I/O.
The conversion of an analog input signal results in a
corresponding 10-bit digital number. The A/D module
has high and low voltage reference input, that is soft-
ware selectable to some combination of VDD, VSS,
RA2, or RA3.
The A/D converter has a unique feature of being able
to operate while the device is in SLEEP mode. To oper-
ate in SLEEP, the A/D clock must be derived from the
A/D’s internal RC oscillator.
Additional information on using the A/D module can be
found in the PICmicro™ Mid-Range MCU Family Ref-
erence Manual (DS33023).
REGISTER 11-1: ADCON0 REGISTER (ADDRESS 1Fh)
R/W-0
R/W-0
R/W-0
CHS2
R/W-0
CHS1
R/W-0
CHS0
R/W-0
R/W-0
ADON
U-0
—
ADCS1
ADCS0
GO/DONE
bit 7
bit 0
bit 7-6
ADCS1:ADCS0: A/D Conversion Clock Select bits (ADCON0 bits in bold)
ADCON1 ADCON0
Clock Conversion
<ADCS2> <ADCS1:ADCS0>
0
0
0
0
1
1
1
1
00
01
10
11
00
01
10
11
FOSC/2
FOSC/8
FOSC/32
FRC (clock derived from the internal A/D RC oscillator)
FOSC/4
FOSC/16
FOSC/64
FRC (clock derived from the internal A/D RC oscillator)
bit 5-3
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= Channel 7 (AN7)
Note: The PIC16F873A/876A devices only implement A/D channels 0 through 4; the unimplemented
selections are reserved. Do not select any unimplemented channels with these devices.
bit 2
GO/DONE: A/D Conversion Status bit
When ADON = 1:
1= A/D conversion in progress (setting this bit starts the A/D conversion which is automatically
cleared by hardware when the A/D conversion is complete)
0= A/D conversion not in progress
bit 1
bit 0
Unimplemented: Read as ’0’
ADON: A/D On bit
1= A/D converter module is powered up
0= A/D converter module is shut-off and consumes no operating current
Legend:
R = Readable bit
W = Writable bit
’1’ = Bit is set
U = Unimplemented bit, read as ‘0’
’0’ = Bit is cleared x = Bit is unknown
- n = Value at POR reset
2001 Microchip Technology Inc.
Advance Information
DS39582A-page 125
MICROCHIP [ MICROCHIP ]
