PIC16CR74ESLASHSP datasheet(89/172 Pages) MICROCHIP

89 / 172 page

DS21993C-page 87

PIC16CR7X

11.2

Selecting the A/D Conversion

Clock

The A/D conversion time per bit is defined as TAD. The

A/D conversion requires 9.0 TAD per 8-bit conversion.

The source of the A/D conversion clock is software

selectable. The four possible options for TAD are:

•2 TOSC (FOSC/2)

•8 TOSC (FOSC/8)

•32 TOSC (FOSC/32)

• Internal RC oscillator (2-6

μs)

For correct A/D conversions, the A/D conversion clock

(TAD) must be selected to ensure a minimum TAD time

as small as possible, but no less than 1.6

μs.

11.3

Configuring Analog Port Pins

The ADCON1, TRISA and TRISE registers control the

operation of the A/D port pins. The port pins that are

desired as analog inputs must have their correspond-

ing TRIS bits set (input). If the TRIS bit is cleared (out-

put), the digital output level (VOH or VOL) will be

converted.

The A/D operation is independent of the state of the

CHS2:CHS0 bits and the TRIS bits.

11.4

A/D Conversions

Setting the GO/DONE bit begins an A/D conversion.

When the conversion completes, the 8-bit result is

placed in the ADRES register, the GO/DONE bit is

cleared, and the ADIF flag (PIR<6>) is set.

If both the A/D interrupt bit ADIE (PIE1<6>) and the

peripheral interrupt enable bit PEIE (INTCON<6>) are

set, the device will wake from Sleep whenever ADIF is

set by hardware. In addition, an interrupt will also occur

if the Global Interrupt bit GIE (INTCON<7>) is set.

Clearing the GO/DONE bit during a conversion will

abort the current conversion. The ADRES register will

NOT be changed and the ADIF flag will not be set.

After the GO/DONE bit is cleared at either the end of a

conversion, or by firmware, another conversion can be

initiated by setting the GO/DONE bit. Users must still

take into account the appropriate acquisition time for

the application.

11.5

A/D Operation During Sleep

The A/D module can operate during Sleep mode. This

requires that the A/D clock source be set to RC

(ADCS1:ADCS0 = 11). When the RC clock source is

selected, the A/D module waits one instruction cycle

before starting the conversion. This allows the SLEEP

instruction to be executed, which eliminates all digital

switching noise from the conversion. When the conver-

sion is completed, the GO/DONE bit will be cleared,

and the result loaded into the ADRES register. If the

A/D interrupt is enabled, the device will wake-up from

Sleep. If the A/D interrupt is not enabled, the A/D

module will then be turned off, although the ADON bit

will remain set.

When the A/D clock source is another clock option (not

RC), a SLEEP instruction will cause the present conver-

sion to be aborted and the A/D module to be turned off,

though the ADON bit will remain set.

Turning off the A/D places the A/D module in its lowest

current consumption state.

11.6

Effects of a Reset

A device Reset forces all registers to their Reset state.

The A/D module is disabled and any conversion in

progress is aborted. All A/D input pins are configured

as analog inputs.

The ADRES register will contain unknown data after a

Power-on Reset.

Note 1: When reading the PORT register, all pins

configured as analog input channels will

read as cleared (a low level). Pins config-

ured as digital inputs will convert an ana-

log input. Analog levels on a digitally

configured input will not affect the conver-

sion accuracy.

2: Analog levels on any pin that is defined as

a digital input, but not as an analog input,

may cause the digital input buffer to

consume current that is out of the

device’s specification.

Note:

The GO/DONE bit should NOT be set in

the same instruction that turns on the A/D.

Note:

For the A/D module to operate in Sleep,

the A/D clock source must be set to RC

(ADCS1:ADCS0 = 11). To perform an A/D

conversion in Sleep, ensure the SLEEP

instruction immediately follows the instruc-

tion that sets the GO/DONE bit.

PIC16CR74E/SP Datasheet(PDF) 89 Page - Microchip Technology

PIC16CR74E/SP Datasheet(HTML) 89 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL