PIC16F7X
11.0
ANALOG-TO-DIGITAL
CONVERTER (A/D) MODULE
The A/D module has three registers. These registers
are:
• A/D Result Register ((ADRES)
• A/D Control Register 0 (ADCON0)
• A/D Control Register 1 ((ADCON1)
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 a voltage reference),
or as digital I/O.
Additional information on using the A/D module can be
found in the PICmicro™ Mid-Range MCU Family Ref-
erence Manual (DS33023) and in Application Note,
AN546 (DS00546).
The 8-bit analog-to-digital (A/D) converter module has
five inputs for the PIC16F73/76 and eight for the
PIC16F74/77.
The A/D allows conversion of an analog input signal to
a corresponding 8-bit digital number. The output of the
sample and hold is the input into the converter, which
generates the result via successive approximation. The
analog reference voltage is software selectable to
either the device’s positive supply voltage (V
DD
), or the
voltage level on the RA3/AN3/V
REF
pin.
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 conversion clock must be
derived from the A/D’s internal RC oscillator.
REGISTER 11-1:
ADCON0 REGISTER (ADDRESS 1Fh)
R/W-0
ADCS1
bit 7
R/W-0
ADCS0
R/W-0
CHS2
R/W-0
CHS1
R/W-0
CHS0
R/W-0
GO/DONE
U-0
—
R/W-0
ADON
bit 0
bit 7-6
ADCS1:ADCS0:
A/D Conversion Clock Select bits
00
= F
OSC
/2
01
= F
OSC
/8
10
= F
OSC
/32
11
= F
RC
(clock derived from the internal A/D module RC oscillator)
CHS2:CHS0:
Analog Channel Select bits
000
= Channel 0 (RA0/AN0)
001
= Channel 1 (RA1/AN1)
010
= Channel 2 (RA2/AN2)
011
= Channel 3 (RA3/AN3)
100
= Channel 4 (RA5/AN4)
101
= Channel 5 (RE0/AN5)
(1)
110
= Channel 6 (RE1/AN6)
(1)
111
= Channel 7 (RE2/AN7)
(1)
GO/DONE:
A/D Conversion Status bit
If ADON = 1:
1
= A/D conversion in progress (setting this bit starts the A/D conversion)
0
= A/D conversion not in progress (this bit is automatically cleared by hardware when the
A/D conversion is complete)
Unimplemented:
Read as '0'
ADON:
A/D On bit
1
= A/D converter module is operating
0
= A/D converter module is shut-off and consumes no operating current
Note 1:
A/D channels 5, 6 and 7 are implemented on the PIC16F74/77 only.
Legend:
R = Readable bit
- n = Value at POR reset
W = Writable bit
’1’ = Bit is set
U = Unimplemented bit, read as ‘0’
’0’ = Bit is cleared
x = Bit is unknown
bit 5-3
bit 2
bit 1
bit 0
2002 Microchip Technology Inc.
DS30325B-page 83
MICROCHIP [ MICROCHIP TECHNOLOGY ]
