PIC18F23K20-ESLASHML datasheet(136/456 Pages) MICROCHIP

136 / 456 page

PIC18F2XK20/4XK20

DS41303G-page 136

 2010 Microchip Technology Inc.

10.7

Port Analog Control

Some port pins are multiplexed with analog functions

such as the Analog-to-Digital Converter and compara-

tors. When these I/O pins are to be used as analog

inputs it is necessary to disable the digital input buffer

to avoid excessive current caused by improper biasing

of the digital input. Individual control of the digital input

buffers on pins which share analog functions is pro-

vided by the ANSEL and ANSELH registers. Setting an

ANSx bit high will disable the associated digital input

buffer and cause all reads of that pin to return ‘0’ while

allowing analog functions of that pin to operate

correctly.

The state of the ANSx bits has no affect on digital

output functions. A pin with the associated TRISx bit

clear and ANSx bit set will still operate as a digital

output but the input mode will be analog. This can

cause unexpected behavior when performing read-

modify-write operations on the affected port.

ANSEL: ANALOG SELECT REGISTER 1

R/W-1

ANS7(1)

ANS6(1)

ANS5(1)

ANS4

ANS3

ANS2

ANS1

ANS0

bit 7

bit 0

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

bit 7

ANS7: RE2 Analog Select Control bit(1)

= Digital input buffer of RE2 is disabled

= Digital input buffer of RE2 is enabled

bit 6

ANS6: RE1 Analog Select Control bit(1)

= Digital input buffer of RE1 is disabled

= Digital input buffer of RE1 is enabled

bit 5

ANS5: RE0 Analog Select Control bit(1)

= Digital input buffer of RE0 is disabled

= Digital input buffer of RE0 is enabled

bit 4

ANS4: RA5 Analog Select Control bit

= Digital input buffer of RA5 is disabled

= Digital input buffer of RA5 is enabled

bit 3

ANS3: RA3 Analog Select Control bit

= Digital input buffer of RA3 is disabled

= Digital input buffer of RA3 is enabled

bit 2

ANS2: RA2 Analog Select Control bit

= Digital input buffer of RA2 is disabled

= Digital input buffer of RA2 is enabled

bit 1

ANS1: RA1 Analog Select Control bit

= Digital input buffer of RA1 is disabled

= Digital input buffer of RA1 is enabled

bit 0

ANS0: RA0 Analog Select Control bit

= Digital input buffer of RA0 is disabled

= Digital input buffer of RA0 is enabled

Note 1:

These bits are not implemented on PIC18F2XK20 devices.

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