PIC16F870_13 Datasheet, PDF (79/172 Pages) Microchip Technology – 28/40-Pin, 8-Bit CMOS FLASH Microcontrollers

PIC16F870/871
10.0 ANALOG-TO-DIGITAL (A/D)
CONVERTER MODULE
The Analog-to-Digital (A/D) Converter module has five
inputs for the 28-pin devices and eight for the other
devices.
The analog input charges a sample and hold capacitor.
The output of the sample and hold capacitor is the input
into the converter. The converter then generates a dig-
ital result of this analog level via successive approxima-
tion. The A/D conversion of the analog input signal
results in a corresponding 10-bit digital number. The
A/D module has high and low voltage reference input
that is software 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.
The A/D module has four registers. These registers
are:
• A/D Result High Register (ADRESH)
• A/D Result Low Register (ADRESL)
• A/D Control Register0 (ADCON0)
• A/D Control Register1 (ADCON1)
The ADCON0 register, shown in Register 10-1, con-
trols the operation of the A/D module. The ADCON1
register, shown in Register 10-2, configures the func-
tions of the port pins. The port pins can be configured
as analog inputs (RA3 can also be the voltage
reference), or as digital I/O.
Additional information on using the A/D module can be
found in the PIC^® Mid-Range MCU Family Reference
Manual (DS33023).
REGISTER 10-1:
ADCON0 REGISTER (ADDRESS: 1Fh)
R/W-0 R/W-0 R/W-0 R/W-0
ADCS1 ADCS0 CHS2
CHS1
bit 7
R/W-0
R/W-0
U-0
CHS0 GO/DONE —
R/W-0
ADON
bit 0
bit 7-6
bit 5-3
bit 2
bit 1
bit 0
ADCS1:ADCS0: A/D Conversion Clock Select bits
00 = FOSC/2
01 = FOSC/8
10 = FOSC/32
11 = FRC (clock derived from the internal A/D module RC oscillator)
CHS2:CHS0: Analog Channel Select bits
000 = Channel 0, (RA0/AN0)
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: These channels are not available on the PIC16F870 device.
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
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DS30569C-page 79