PIC16C9XX Datasheet, PDF (79/189 Pages) Microchip Technology – 8-Bit CMOS Microcontroller with LCD Driver

12.0 ANALOG-TO-DIGITAL
CONVERTER (A/D) MODULE
This section applies to the PIC16C924 only.
The analog-to-digital (A/D) converter module has five
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 AVDD pin or the voltage level
on the RA3/AN3/VREF 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.
PIC16C9XX
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 Figure 12-1, controls
the operation of the A/D module. The ADCON1 regis-
ter, shown in Figure 12-2, configures the functions of
the port pins. The port pins can be configured as ana-
log inputs (RA3 can also be a voltage reference) or as
digital I/O.
FIGURE 12-1: ADCON0 REGISTER (ADDRESS 1Fh)
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
ADCS1 ADCS0 CHS2 CHS1 CHS0 GO/DONE —
bit7
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 RC oscillation)
ADON
bit0
R = Readable bit
W = Writable bit
U = Unimplemented bit,
read as ‘0’
- n = Value at POR reset
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: Reserved: Always maintain this bit clear
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
© 1997 Microchip Technology Inc.
DS30444E - page 79