PIC16F631 datasheet(111/294 Pages) MICROCHIP

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DS41262D-page 109

PIC16F631/677/685/687/689/690

TABLE 9-1:

ADC CLOCK PERIOD (TAD) VS. DEVICE OPERATING FREQUENCIES (VDD > 3.0V)

FIGURE 9-2:

ANALOG-TO-DIGITAL CONVERSION TAD CYCLES

9.1.5

INTERRUPTS

The ADC module allows for the ability to generate an

interrupt upon completion of an Analog-to-Digital

conversion. The ADC interrupt flag is the ADIF bit in the

PIR1 register. The ADC interrupt enable is the ADIE bit

in the PIE1 register. The ADIF bit must be cleared in

software.

This interrupt can be generated while the device is

operating or while in Sleep. If the device is in Sleep, the

interrupt will wake-up the device. Upon waking from

Sleep, the next instruction following the SLEEP

instruction is always executed. If the user is attempting

to wake-up from Sleep and resume in-line code

execution, the global interrupt must be disabled. If the

global interrupt is enabled, execution will switch to the

interrupt service routine.

Please see Section 9.1.5 “Interrupts” for more

information.

ADC Clock Period (TAD)

Device Frequency (FOSC)

ADC Clock Source

ADCS<2:0>

20 MHz

8 MHz

4 MHz

1 MHz

FOSC/2

000

100 ns(2)

250 ns(2)

500 ns(2)

2.0

μs

FOSC/4

100

200 ns(2)

500 ns(2)

1.0

μs(2)

4.0

μs

FOSC/8

001

400 ns(2)

1.0

μs(2)

2.0

μs

8.0

μs(3)

FOSC/16

101

800 ns(2)

2.0

μs4.0 μs

16.0

μs(3)

FOSC/32

010

1.6

μs4.0 μs

8.0

μs(3)

32.0

μs(3)

FOSC/64

110

3.2

μs

8.0

μs(3)

16.0

μs(3)

64.0

μs(3)

FRC

x11

2-6

μs(1,4)

2-6

μs(1,4)

2-6

μs(1,4)

2-6

μs(1,4)

Legend: Shaded cells are outside of recommended range.

Note 1:

The FRC source has a typical TAD time of 4

μs for VDD > 3.0V.

These values violate the minimum required TAD time.

For faster conversion times, the selection of another clock source is recommended.

When the device frequency is greater than 1 MHz, the FRC clock source is only recommended if the

conversion will be performed during Sleep.

TAD1 TAD2 TAD3 TAD4 TAD5 TAD6 TAD7 TAD8 TAD9

Set GO/DONE bit

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

TAD10 TAD11

TCY to TAD

Conversion Starts

ADRESH and ADRESL registers are loaded,

GO bit is cleared,

ADIF bit is set,

Holding capacitor is connected to analog input

Note:

The ADIF bit is set at the completion of

every conversion, regardless of whether

or not the ADC interrupt is enabled.

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