PIC16C745/765
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 dedicated internal RC oscillator.
12.0 ANALOG-TO-DIGITAL
CONVERTER (A/D) MODULE
The 8-bit Analog-To-Digital (A/D) converter module has
five inputs for the PIC16C745 and eight for the
PIC16C765.
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 A/D allows conversion of an analog input signal to
a corresponding 8-bit digital value. 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 (VDD) or the
voltage level on the RA3/AN3/VREF pin.
The ADCON0 register, shown in Register 12-1, con-
trols the operation of the A/D module. The ADCON1
register, shown in Register 12-2, 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.
REGISTER 12-1: A/D CONTROL REGISTER (ADCON0: 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: ADCS<1:0>: A/D Conversion Clock Select bits
00= FINT/2
01= FINT/8
10= FINT/32
11= FRC (clock derived from dedicated internal oscillator)
bit 5-3: CHS<2:0>: 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)
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 conver-
sion 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
Note 1: A/D channels 5, 6 and 7 are implemented on the PIC16C765 only.
1999 Microchip Technology Inc.
Advanced Information
DS41124A-page 89
MICROCHIP [ MICROCHIP ]
