PIC16C62B/72A
Additional information on the A/D module is available in
the PICmicro™ Mid-Range Reference Manual,
(DS33023).
9.0
ANALOG-TO-DIGITAL
CONVERTER (A/D) MODULE
Note: This section applies to the PIC16C72A
The A/D module has three registers. These registers
are:
only.
The analog-to-digital (A/D) converter module has five
input channels.
• A/D Result Register (ADRES)
• A/D Control Register 0 (ADCON0)
• A/D Control Register 1 (ADCON1)
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 (VDD)
or the voltage level on the RA3/AN3/VREF pin.
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 9-1, controls
the operation of the A/D module. The ADCON1 regis-
ter, shown in Figure 9-2, 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 dig-
ital I/O.
The A/D converter has the 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.
REGISTER 9-1:ADCON0 REGISTER (ADDRESS 1Fh)
R/W-0 R/W-0 R/W-0
ADCS1 ADCS0 CHS2
bit7
R/W-0
CHS1
R/W-0
R/W-0
U-0
—
R/W-0
ADON
CHS0 GO/DONE
R =Readable bit
W = Writable bit
U =Unimplemented bit,
read as ‘0’
bit0
- n = Value at POR reset
bit 7-6: ADCS1:ADCS0: A/D Conversion Clock Select bits
00= FOSC/2
01= FOSC/8
10= FOSC/32
11= FRC (clock derived from an internal 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)
100= channel 4, (RA5/AN4)
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:
bit 0:
Unimplemented: Read as '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
1999 Microchip Technology Inc.
Preliminary
DS35008B-page 49
MICROCHIP [ MICROCHIP ]
