Datasheet

 1999-2013 Microchip Technology Inc. DS41106C-page 45
PIC16C712/716
8.0 ANALOG-TO-DIGITAL
CONVERTER (A/D) MODULE
The Analog-to-Digital (A/D) Converter module has four
inputs.
The A/D allows conversion of an analog input signal to
a corresponding 8-bit digital number (refer to Applica-
tion Note AN546 for use of A/D Converter). The output
of the sample and hold is the input into the converter,
which generates the result via successive approxima-
tion. The analog reference voltage is software select-
able 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
operate in Sleep, the A/D conversion clock must be
derived from the A/D’s internal RC oscillator.
Additional information on the A/D module is available in
the PIC
®
Mid-Range Reference Manual, (DS33023).
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)
A device Reset forces all registers to their Reset state.
This forces the A/D module to be turned off, and any
conversion is aborted.
The ADCON0 register, shown in Figure 8-1, controls
the operation of the A/D module. The ADCON1 regis-
ter, shown in Figure 8-2, configures the functions 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.
FIGURE 8-1: ADCON0 REGISTER (ADDRESS 1Fh)
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 U-0 R/W-0
ADCS1 ADCS0 CHS2 CHS1 CHS0 GO/DONE
— ADON R =Readable bit
W = Writable bit
U =Unimplemented bit,
read as ‘0’
-n = Value at POR Reset
bit7 bit0
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 ADC RC oscillator)
bit 5-3: 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)
1xx = reserved, do not use
bit 2: 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)
bit 1: Unimplemented: Read as ‘0’
bit 0: ADON: A/D On bit
1 = A/D converter module is operating
0 = A/D converter module is shutoff and consumes no operating current