Datasheet

PIC18F2420/2520/4420/4520
DS39631E-page 232 © 2008 Microchip Technology Inc.
19.8 Use of the CCP2 Trigger
An A/D conversion can be started by the Special Event
Trigger of the CCP2 module. This requires that the
CCP2M<3:0> bits (CCP2CON<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 (or Timer3) counter will be reset to zero.
Timer1 (or Timer3) 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 is 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 (or Timer3)
counter.
TABLE 19-2: 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 49
PIR1
PSPIF
(1)
ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 52
PIE1
PSPIE
(1)
ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 52
IPR1 PSPIP
(1)
ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 52
PIR2
OSCFIF CMIF — EEIF BCLIF HLVDIF TMR3IF CCP2IF 52
PIE2
OSCFIE CMIE — EEIE BCLIE HLVDIE TMR3IE CCP2IE 52
IPR2 OSCFIP CMIP — EEIP BCLIP HLVDIP TMR3IP CCP2IP 52
ADRESH A/D Result Register High Byte 51
ADRESL A/D Result Register Low Byte 51
ADCON0
— — CHS3 CHS2 CHS1 CHS0 GO/DONE ADON 51
ADCON1 — — VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 51
ADCON2 ADFM
— ACQT2 ACQT1 ACQT0 ADCS2 ADCS1 ADCS0 51
PORTA RA7
(2)
RA6
(2)
RA5 RA4 RA3 RA2 RA1 RA0 52
TRISA TRISA7
(2)
TRISA6
(2)
PORTA Data Direction Register 52
PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 52
TRISB PORTB Data Direction Register 52
LATB PORTB Data Latch Register (Read and Write to Data Latch) 52
PORTE
(4)
— — — —RE3
(3)
RE2 RE1 RE0 52
TRISE
(4)
IBF OBF IBOV PSPMODE — TRISE2 TRISE1 TRISE0 52
LATE
(4)
— — — — — PORTE Data Latch Register 52
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for A/D conversion.
Note 1: These bits are unimplemented on 28-pin devices; always maintain these bits clear.
2: PORTA<7:6> and their direction bits are individually configured as port pins based on various primary
oscillator modes. When disabled, these bits read as ‘0’.
3: RE3 port bit is available only as an input pin when the MCLRE Configuration bit is ‘0’.
4: These registers are not implemented on 28-pin devices.