PIC12CE67X Datasheet, PDF (37/116 Pages) Microchip Technology – 8-Pin, 8-Bit CMOS Microcontroller with A/D Converter and EEPROM Data Memory

PIC12CE67X
8.0 ANALOG-TO-DIGITAL
CONVERTER (A/D) MODULE
The analog-to-digital (A/D) converter module has four
analog 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 positive supply voltage (VDD)
or the voltage level on the GP1/AN1/VREF pin. The A/D
converter has a unique feature of being able to operate
while the device is in SLEEP mode.
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 8-1, controls
the operation of the A/D module. The ADCON1 regis-
ter, shown in Figure 8-2, configures the functions of the
port pins. The port pins can be configured as analog
inputs (GP1 can also be a voltage reference) or as dig-
ital I/O.
Note:
Note:
If the port pins are configured as analog
inputs (reset condition), reading the port
(MOVF GP,W) results in reading '0's.
Changing ADCON1 register can cause the
GPIF and INTF flags to be set in the
INTCON register. These interrupts should
be disabled prior to modifying ADCON1.
FIGURE 8-1: ADCON0 REGISTER (ADDRESS 1Fh)
R/W-0 R/W-0
ADCS1 ADCS0
bit7
R/W-0
r
R/W-0
CHS1
R/W-0 R/W-0 R/W-0
CHS0 GO/DONE
r
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)
R/W-0
ADON
bit0
R = Readable bit
W = Writable bit
U = Unimplemented bit,
read as ‘0’
- n = Value at POR reset
bit 5: Reserved
bit 4-3: CHS1:CHS0: Analog Channel Select bits
00 = channel 0, (GP0/AN0)
01 = channel 1, (GP1/AN1)
10 = channel 2, (GP2/AN2)
11 = channel 3, (GP4/AN3)
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: Reserved
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.
Preliminary
DS40181B-page 37