PIC17C75X Datasheet, PDF (167/320 Pages) Microchip Technology – High-Performance 8-Bit CMOS EPROM Microcontrollers

PIC17C75X
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.
The A/D allows conversion of an analog input signal to
a corresponding 10-bit digital number. The output of the
sample and hold is the input into the converter, which
generates the result via successive approximation.
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
CHS3
bit7
R/W-0
CHS2
R/W-0
CHS1
R/W-0
CHS0
U-0
R/W-0
U-0
— GO/DONE —
bit 7-4: CHS2: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)
11xx = RESERVED, do not select
R/W-0
ADON
bit0
R = Readable bit
W = Writable bit
U = Unimplemented bit,
read as ‘0’
- n = Value at POR reset
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
© 1997 Microchip Technology Inc.
Preliminary
DS30264A-page 167