PIC16F72SLASHSS datasheet(59/136 Pages) MICROCHIP

59 / 136 page

 2002 Microchip Technology Inc.

DS39597B-page 57

PIC16F72

10.5

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 mod-

ule 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.

10.6

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.

10.7

Use of the CCP Trigger

An A/D conversion can be started by the “special event

trigger” of the CCP1 module. This requires that the

CCP1M3:CCP1M0 bits (CCP1CON<3:0>) be pro-

grammed as 1011 and that the A/D module is enabled

(ADON bit is set). When the trigger occurs, the

GO/DONE bit will be set, starting the A/D conversion,

and the Timer1 counter will be reset to zero. Timer1 is

reset to automatically repeat the A/D acquisition period

with minimal software overhead (moving the ADRES to

the desired location). The appropriate analog input

channel must be selected and the minimum acquisition

done before the “special event trigger” sets the

GO/DONE bit (starts a conversion).

If the A/D module is not enabled (ADON is cleared),

then the “special event trigger” will be ignored by the

A/D module, but will still reset the Timer1 counter.

TABLE 10-2:

REGISTERS/BITS ASSOCIATED WITH 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

instruction that sets the GO/DONE bit.

Address

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Value on

POR, BOR

Value on

all other

RESETS

0Bh,8Bh

10Bh,18Bh

INTCON

GIE

PEIE

TMR0IE

INTE

RBIE

TMR0IF

INTF

RBIF

0000 000x

0000 000u

0Ch

PIR1

—

ADIF

—

SSPIF

CCP1IF

TMR2IF TMR1IF

-0-- 0000

8Ch

PIE1

—

ADIE

—

SSPIE

CCP1IE

TMR2IE TMR1IE -0-- 0000

-0-- 0000

1Eh

ADRES

A/D Result Register

xxxx xxxx

uuuu uuuu

1Fh

ADCON0

ADCS1 ADCS0

CHS2

CHS1

CHS0

GO/DONE

—

ADON

0000 00-0

9Fh

ADCON1

—

PCFG2

PCFG1

PCFG0

---- -000

05h

PORTA

—

RA5

RA4

RA3

RA2

RA1

RA0

--0x 0000

--0u 0000

85h

TRISA

—

PORTA Data Direction Register

--11 1111

Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’. Shaded cells are not used for A/D conversion.

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