PIC18F23K20-ESLASHPSQTP datasheet(260/420 Pages) MICROCHIP

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PIC18F2XK20/4XK20

DS41303B-page 258

Advance Information

19.2

ADC Operation

19.2.1

STARTING A CONVERSION

To enable the ADC module, the ADON bit of the

ADCON0 register must be set to a ‘1’. Setting the GO/

DONE bit of the ADCON0 register to a ‘1’ will, depend-

ing on the ACQT bits of the ADCON2 register, either

immediately start the Analog-to-Digital conversion or

start an acquisition delay followed by the Analog-to-

Digital conversion.

Figure 19-3 shows the operation of the A/D converter

after the GO bit has been set and the ACQT<2:0> bits

are cleared. A conversion is started after the following

instruction to allow entry into SLEEP mode before the

conversion begins.

Figure 19-4 shows the operation of the A/D converter

after the GO bit has been set and the ACQT<2:0> bits

are set to ‘010’ which selects a 4 TAD acquisition time

before the conversion starts.

FIGURE 19-3:

A/D CONVERSION TAD CYCLES (ACQT<2:0> = 000, TACQ = 0)

FIGURE 19-4:

A/D CONVERSION TAD CYCLES (ACQT<2:0> = 010, TACQ = 4 TAD)

Note:

The GO/DONE bit should not be set in the

same instruction that turns on the ADC.

Refer to Section 19.2.9 “A/D Conver-

sion Procedure”.

TAD1 TAD2 TAD3 TAD4 TAD5 TAD6 TAD7 TAD8

TAD11

Set GO bit

Holding capacitor is disconnected from analog input (typically 100 ns)

TAD9 TAD10

TCY - TAD

ADRESH:ADRESL is loaded, GO bit is cleared,

ADIF bit is set, holding capacitor is connected to analog input.

Conversion starts

On the following cycle:

2 TAD

Discharge

Set GO bit

(Holding capacitor is disconnected from analog input)

Conversion starts

(Holding capacitor continues

acquiring input)

TACQT Cycles

TAD Cycles

Automatic

Acquisition

Time

ADRESH:ADRESL is loaded, GO bit is cleared,

ADIF bit is set, holding capacitor is connected to analog input.

On the following cycle:

2 TAD

Discharge

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