PIC17C7XX Datasheet, PDF (177/328 Pages) Microchip Technology – High-Performance 8-Bit CMOS EPROM Microcontrollers with 10-bit A/D

PIC17C7XX
16.0 ANALOG-TO-DIGITAL
CONVERTER (A/D) MODULE
The analog-to-digital (A/D) converter module has
twelve analog inputs for the PIC17C75X devices and
sixteen for the PIC17C76X 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. This A/D conversion, of the analog input signal,
results in a corresponding 10-bit digital number.
The analog reference voltages (positive and negative
supply) are software selectable to either the device’s
supply voltages (AVDD, AVss) or the voltage level on
the RG3/AN0/VREF+ and RG2/AN1/VREF- pins.
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 Figure 16-1, controls
the operation of the A/D module. The ADCON1 regis-
ter, shown in Figure 16-2, configures the functions of
the port pins. The port pins can be configured as ana-
log inputs (RG3 and RG2 can also be the voltage refer-
ences) or as digital I/O.
FIGURE 16-1: ADCON0 REGISTER (ADDRESS: 14h, BANK 5)
R/W-0 R/W-0 R/W-0 R/W-0 U-0
R/W-0
U-0
R/W-0
CHS3 CHS2 CHS1 CHS0
bit7
— GO/DONE —
ADON
bit0
R = Readable bit
W = Writable bit
U = Unimplemented bit,
read as ‘0’
- n = Value at POR reset
bit 7-4: CHS3:CHS0: Analog Channel Select bits
0000 = channel 0, (AN0)
0001 = channel 1, (AN1)
0010 = channel 2, (AN2)
0011 = channel 3, (AN3)
0100 = channel 4, (AN4)
0101 = channel 5, (AN5)
0110 = channel 6, (AN6)
0111 = channel 7, (AN7)
1000 = channel 8, (AN8)
1001 = channel 9, (AN9)
1010 = channel 10, (AN10)
1011 = channel 11, (AN11)
1100 = channel 12, (AN12) (PIC17C76X only)
1101 = channel 13, (AN13) (PIC17C76X only)
1110 = channel 14, (AN14) (PIC17C76X only)
1111 = channel 15, (AN15) (PIC17C76X only)
11xx = RESERVED, do not select (PIC17C75X only)
bit 3: Unimplemented: Read as '0'
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 which is automatically cleared
by hardware when the A/D conversion is complete)
0 = A/D conversion not in progress
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
© 1998 Microchip Technology Inc.
DS30289A-page 177