PIC18LF4331 datasheet(253/392 Pages) MICROCHIP

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 2010 Microchip Technology Inc.

DS39616D-page 253

PIC18F2331/2431/4331/4431

21.9

A/D Conversions

Figure 21-3 shows the operation of the A/D Converter

after the GO/DONE 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. The internal A/D

RC oscillator must be selected to perform a conversion

in Sleep.

Figure 21-4 shows the operation of the A/D Converter

after the GO/DONE bit has been set, the ACQT<3:0>

bits are set to ‘010’ and a 4 TAD acquisition time is

selected before the conversion starts.

Clearing the GO/DONE bit during a conversion will

abort the current conversion. The resulting buffer loca-

tion will contain the partially completed A/D conversion

sample. This will not set the ADIF flag, therefore, the

user must read the buffer location before a conversion

sequence overwrites it.

After the A/D conversion is completed or aborted, a

2TAD wait is required before the next acquisition can be

started. After this wait, acquisition on the selected

channel is automatically started.

FIGURE 21-3:

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

FIGURE 21-4:

A/D CONVERSION TAD CYCLES (ACQT<3:0> = 0010, TACQ = 4 TAD)

Note:

The GO/DONE bit should NOT be set in

the same instruction that turns on the A/D.

TAD1 TAD2 TAD3 TAD4 TAD5 TAD6 TAD7 TAD8

TAD11

TAD9 TAD10

GO/DONE bit cleared on the rising edge of Q1 after the first Q3

Conversion Starts

following TAD11 and result buffer is loaded.(1)

GO/DONE bit is

set and holding

cap is

disconnected

from analog

input

Note 1:

Conversion time is a minimum of 11 TAD + 2 TCY and a maximum of 11 TAD + 6 TCY.

A/D Triggered

(Holding capacitor is disconnected)

TACQT Cycles

Automatic

Acquisition

Time

TAD1 TAD2 TAD3 TAD4 TAD5 TAD6 TAD7 TAD8

TAD11

TAD9 TAD10

GO/DONE bit cleared on the rising edge of Q1 after the first Q3

Conversion Starts

following TAD11 and result buffer is loaded.(1)

TAD Cycles

Note 1:

In Continuous modes, next conversion starts at the end of TAD12.

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