Datasheet

PIC18F2420/2520/4420/4520
DS39631E-page 134 © 2008 Microchip Technology Inc.
13.2 Timer2 Interrupt
Timer2 also can generate an optional device interrupt.
The Timer2 output signal (TMR2 to PR2 match) pro-
vides the input for the 4-bit output counter/postscaler.
This counter generates the TMR2 match interrupt flag
which is latched in TMR2IF (PIR1<1>). The interrupt is
enabled by setting the TMR2 Match Interrupt Enable
bit, TMR2IE (PIE1<1>).
A range of 16 postscale options (from 1:1 through 1:16
inclusive) can be selected with the postscaler control
bits, T2OUTPS<3:0> (T2CON<6:3>).
13.3 Timer2 Output
The unscaled output of TMR2 is available primarily to
the CCP modules, where it is used as a time base for
operations in PWM mode.
Timer2 can optionally be used as the shift clock source
for the MSSP module operating in SPI mode. Addi-
tional information is provided in Section 17.0 “Master
Synchronous Serial Port (MSSP) Module”.
FIGURE 13-1: TIMER2 BLOCK DIAGRAM
TABLE 13-1: REGISTERS ASSOCIATED WITH TIMER2 AS A TIMER/COUNTER
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
TMR2 Timer2 Register 50
T2CON
— T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 50
PR2 Timer2 Period Register 50
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Timer2 module.
Note 1: These bits are unimplemented on 28-pin devices; always maintain these bits clear.
Comparator
TMR2 Output
TMR2
Postscaler
Prescaler
PR2
2
F
OSC/4
1:1 to 1:16
1:1, 1:4, 1:16
4
T2OUTPS<3:0>
T2CKPS<1:0>
Set TMR2IF
Internal Data Bus
8
Reset
TMR2/PR2
8
8
(to PWM or MSSP)
Match