PIC18F2450/4450
DS39760A-page 182
Advance Information
2006 Microchip Technology Inc.
16.8
Use of the CCP1 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
programmed 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 acquisition
and 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 ADRESH:ADRESL to the desired location).
The appropriate analog input channel must be selected
and the minimum acquisition period is either timed by
the user, or an appropriate TACQ time selected before
the Special Event Trigger sets the GO/DONE bit (starts
a conversion).
If the A/D module is not enabled (ADON is cleared), the
Special Event Trigger will be ignored by the A/D
module but will still reset the Timer1 counter.
TABLE 16-2:
REGISTERS ASSOCIATED WITH A/D OPERATION
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Reset
Values
on page
INTCON
GIE/GIEH PEIE/GIEL
TMR0IE
INT0IE
RBIE
TMR0IF
INT0IF
RBIF
PIR1
—
ADIF
RCIF
TXIF
—
CCP1IF
TMR2IF
TMR1IF
PIE1
—
ADIE
RCIE
TXIE
—
CCP1IE
TMR2IE
TMR1IE
IPR1
—
ADIP
RCIP
TXIP
—
CCP1IP
TMR2IP
TMR1IP
PIR2
OSCFIF
—
USBIF
—
HLVDIF
—
PIE2
OSCFIE
—
USBIE
—
HLVDIE
—
IPR2
OSCFIP
—
USBIP
—
HLVDIP
—
ADRESH
A/D Result Register High Byte
ADRESL
A/D Result Register Low Byte
ADCON0
—
CHS3
CHS2
CHS1
CHS0
GO/DONE
ADON
ADCON1
—
VCFG1
VCFG0
PCFG3
PCFG2
PCFG1
PCFG0
ADCON2
ADFM
—
ACQT2
ACQT1
ACQT0
ADCS2
ADCS1
ADCS0
PORTA
—RA6(2)
RA5
RA4
RA3
RA2
RA1
RA0
TRISA
—
TRISA6(2)
TRISA5
TRISA4
TRISA3
TRISA2
TRISA1
TRISA0
PORTB
RB7
RB6
RB5
RB4
RB3
RB2
RB1
RB0
TRISB
TRISB7
TRISB6
TRISB5
TRISB4
TRISB3
TRISB2
TRISB1
TRISB0
LATB
LATB7
LATB6
LATB5
LATB4
LATB3
LATB2
LATB1
LATB0
PORTE
—
—RE3(1,3)
RE2(4)
RE1(4)
RE0(4)
TRISE(4)
—
TRISE2(4) TRISE1(4) TRISE0(4)
LATE(4)
—
—LATE2(4)
LATE1(4)
LATE0(4)
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for A/D conversion.
Note 1:
Implemented only when Master Clear functionality is disabled (MCLRE Configuration bit = 0).
2:
RA6 and its associated latch and data direction bits are enabled as I/O pins based on oscillator
configuration; otherwise, they are read as ‘0’.
3:
RE3 port bit is available only as an input pin when the MCLRE Configuration bit is ‘0’.
4:
These registers and/or bits are not implemented on 28-pin devices.