Microchip Technology DM164134 数据表
© 2006 Microchip Technology Inc.
DS41159E-page 241
PIC18FXX8
20.0
COMPATIBLE 10-BIT ANALOG-
TO-DIGITAL CONVERTER (A/D)
MODULE
TO-DIGITAL CONVERTER (A/D)
MODULE
The Analog-to-Digital (A/D) Converter module has five
inputs for the PIC18F2X8 devices and eight for the
PIC18F4X8 devices. This module has the ADCON0
and ADCON1 register definitions that are compatible
with the PICmicro
inputs for the PIC18F2X8 devices and eight for the
PIC18F4X8 devices. This module has the ADCON0
and ADCON1 register definitions that are compatible
with the PICmicro
®
mid-range A/D module.
The A/D allows conversion of an analog input signal to
a corresponding 10-bit digital number.
a corresponding 10-bit digital number.
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 Register 0 (ADCON0)
• A/D Control Register 1 (ADCON1)
The ADCON0 register, shown in Register 20-1,
controls the operation of the A/D module. The
ADCON1 register, shown in Register 20-2, configures
the functions of the port pins.
controls the operation of the A/D module. The
ADCON1 register, shown in Register 20-2, configures
the functions of the port pins.
REGISTER 20-1:
ADCON0: A/D CONTROL REGISTER 0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
U-0
R/W-0
ADCS1
ADCS0
CHS2
CHS1
CHS0
GO/DONE
—
ADON
bit 7
bit 0
bit 7-6
ADCS1:ADCS0: A/D Conversion Clock Select bits (ADCON0 bits in bold)
bit 5-3
CHS2:CHS0: Analog Channel Select bits
000
= Channel 0 (AN0)
001
= Channel 1 (AN1)
010
= Channel 2 (AN2)
011
= Channel 3 (AN3)
100
= Channel 4 (AN4)
101
= Channel 5 (AN5)
(1)
110
= Channel 6 (AN6)
(1)
111
= Channel 7 (AN7)
(1)
Note 1: These channels are unimplemented on PIC18F2X8 (28-pin) devices. Do not select
any unimplemented channel.
bit 2
GO/DONE: A/D Conversion Status bit
When ADON = 1:
When 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 powered up
0
= A/D converter module is shut-off and consumes no operating current
Legend:
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
x = Bit is unknown
ADCON1
<ADCS2>
ADCON0
<ADCS1:ADCS0>
Clock Conversion
0
00
F
OSC
/2
0
01
F
OSC
/8
0
10
F
OSC
/32
0
11
F
RC
(clock derived from the internal A/D RC oscillator)
1
00
F
OSC
/4
1
01
F
OSC
/16
1
10
F
OSC
/64
1
11
F
RC
(clock derived from the internal A/D RC oscillator)