PIC16F87_05 Datasheet, PDF (122/228 Pages) Microchip Technology – 18/20/28-Pin Enhanced Flash Microcontrollers with nanoWatt Technology

PIC16F87/88
12.6 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 registers. 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.
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.
12.7 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 value that is in the ADRESH:ADRESL registers
is not modified for a Power-on Reset. The
ADRESH:ADRESL registers will contain unknown data
after a Power-on Reset.
12.8 Use of the CCP Trigger
An A/D conversion can be started by the “special event
trigger” of the CCP 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
ADRESH:ADRESL to the desired location). The appro-
priate 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 12-2: REGISTERS/BITS ASSOCIATED WITH A/D
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
0Ch
8Ch
1Eh
9Eh
INTCON
GIE PEIE TMR0IE INT0IE RBIE
PIR1
PIE1
ADRESH⁽²⁾
ADRESL⁽²⁾
— ADIF⁽¹⁾ RCIF TXIF
— ADIE⁽¹⁾ RCIE TXIE
A/D Result Register High Byte
A/D Result Register Low Byte
SSPIF
SSPIE
TMR0IF INT0IF RBIF 0000 000x 0000 000u
CCP1IF TMR2IF TMR1IF -000 0000 -000 0000
CCP1IE TMR2IE TMR1IE -000 0000 -000 0000
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
1Fh
ADCON0⁽²⁾ ADCS1 ADCS0 CHS2 CHS1 CHS0 GO/DONE —
ADON 0000 00-0 0000 00-0
9Fh
ADCON1⁽²⁾ ADFM ADCS2 VCFG1 VCFG0 —
—
—
— 0000 ---- 0000 ----
9Bh
ANSEL⁽²
— ANS6 ANS5 ANS4 ANS3 ANS2 ANS1 ANS0 -111 1111 -111 1111
05h
PORTA
RA7 RA6
RA5
RA4 RA3
RA2
RA1 RA0
(PIC16F87)
xxxx 0000 uuuu 0000
(PIC16F88)
xxx0 0000 uuu0 0000
05h, 106h
85h
PORTB
RB7
(PIC16F87)
(PIC16F88)
TRISA
TRISA7
RB6
RB5
RB4 RB3
RB2
RB1 RB0
TRISA6 TRISA5⁽³⁾ PORTA Data Direction Register (TRISA<4:0>)
xxxx xxxx uuuu uuuu
00xx xxxx 00uu uuuu
1111 1111 1111 1111
86h, 186h TRISB
TRISB7 TRISB6 TRISB5 TRISB4 TRISB3 TRISB2 TRISB1 TRISB0 1111 1111 1111 1111
Legend:
Note 1:
2:
3:
x = unknown, u = unchanged, - = unimplemented, read as ‘0’. Shaded cells are not used for A/D conversion.
This bit is only implemented on the PIC16F88. The bit will read ‘0’ on the PIC16F87.
PIC16F88 only.
Pin 5 is an input only; the state of the TRISA5 bit has no effect and will always read ‘1’.
DS30487C-page 120
 2005 Microchip Technology Inc.