PIC18LF2523-I/SO 查看數據表（PDF） - Microchip Technology

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PIC18LF2523-I/SO

28/40/44-Pin, Enhanced Flash Microcontrollers with 12-Bit A/D and nanoWatt Technology

Microchip Technology 

PIC18F2423/2523/4423/4523

The value in the ADRESH:ADRESL registers is

unknown following POR and BOR Resets and is not

affected by any other Reset.

After the A/D module has been configured as desired,

the selected channel must be acquired before the

conversion is started. The analog input channels must

have their corresponding TRIS bits selected as inputs.

To determine acquisition time, see Section 2.1 “A/D

Acquisition Requirements”.

After this acquisition time has elapsed, the A/D conver-

sion can be started. An acquisition time can be

programmed to occur between setting the GO/DONE

bit and the actual start of the conversion.

The following steps should be followed to perform an A/D

conversion:

1. Configure the A/D module:

• Configure analog pins, voltage reference and

digital I/O (ADCON1)

• Select A/D input channel (ADCON0)

• Select A/D acquisition time (ADCON2)

• Select A/D conversion clock (ADCON2)

• Turn on the A/D module (ADCON0)

2. Configure the A/D interrupt (if desired):

• Clear ADIF bit

• Set ADIE bit

• Set GIE bit

3. Wait the required acquisition time (if required).

4. Start conversion by setting the GO/DONE bit

(ADCON0<1>).

5. Wait for the A/D conversion to complete by either:

• Polling for the GO/DONE bit to be cleared

OR

• Waiting for the A/D interrupt

6. Read the A/D Result registers (ADRESH:ADRESL)

and clear the ADIF bit, if required.

7. For the next conversion, go to step 1 or step 2,

as required.

The A/D conversion time per bit is defined as

TAD. A minimum wait of 2 TAD is required before

the next acquisition starts.

FIGURE 2-2:

A/D TRANSFER FUNCTION

FFFh

FFEh

003h

002h

001h

000h

Analog Input Voltage

FIGURE 2-3:

ANALOG INPUT MODEL

VDD

Rs ANx

VT = 0.6V

RIC ≤ 1k

Sampling

Switch

SS RSS

VAIN

CPIN

5 pF

VT = 0.6V

ILEAKAGE

±100 nA

CHOLD = 25 pF

VSS

Legend: CPIN

= Input Capacitance

VT

= Threshold Voltage

ILEAKAGE = Leakage Current at the pin due to

various junctions

RIC

= Interconnect Resistance

SS

= Sampling Switch

CHOLD = Sample/Hold Capacitance (from DAC)

RSS

= Sampling Switch Resistance

6V

5V

VDD 4V

3V

2V

1 23 4

Sampling Switch (kΩ)

© 2009 Microchip Technology Inc.

DS39755C-page 29

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