PIC18F45K80-I Datasheet, PDF (221/622 Pages) Microchip Technology – 28/40/44/64-Pin, Enhanced Flash Microcontrollers with ECAN and nanoWatt XLP Technology

PIC18F66K80 FAMILY
15.0 TIMER2 MODULE
The Timer2 module incorporates the following features:
• Eight-bit Timer and Period registers (TMR2 and
PR2, respectively)
• Both registers are readable and writable
• Software programmable prescaler
(1:1, 1:4 and 1:16)
• Software programmable postscaler
(1:1 through 1:16)
• Interrupt on TMR2 to PR2 match
• Optional use as the shift clock for the
MSSP module
The module is controlled through the T2CON register
(Register 15-1) that enables or disables the timer, and
configures the prescaler and postscaler. Timer2 can be
shut off by clearing control bit, TMR2ON (T2CON<2>),
to minimize power consumption.
A simplified block diagram of the module is shown in
Figure 15-1.
15.1 Timer2 Operation
In normal operation, TMR2 is incremented from 00h on
each clock (FOSC/4). A four-bit counter/prescaler on the
clock input gives the prescale options of direct input,
divide-by-4 or divide-by-16. These are selected by the
prescaler control bits, T2CKPS<1:0> (T2CON<1:0>).
The value of TMR2 is compared to that of the Period reg-
ister, PR2, on each clock cycle. When the two values
match, the comparator generates a match signal as the
timer output. This signal also resets the value of TMR2
to 00h on the next cycle and drives the output counter/
postscaler. (See Section 15.2 “Timer2 Interrupt”.)
The TMR2 and PR2 registers are both directly readable
and writable. The TMR2 register is cleared on any
device Reset, while the PR2 register initializes at FFh.
Both the prescaler and postscaler counters are cleared
on the following events:
• A write to the TMR2 register
• A write to the T2CON register
• Any device Reset – Power-on Reset (POR),
MCLR Reset, Watchdog Timer Reset (WDTR) or
Brown-out Reset (BOR)
TMR2 is not cleared when T2CON is written.
Note:
The CCP and ECCP modules use Timers,
1 through 4, for some modes. The assign-
ment of a particular timer to a CCP/ECCP
module is determined by the Timer to CCP
enable bits in the CCPTMRS register. For
more details, see Register 20-2 and
Register 19-2.
REGISTER 15-1: T2CON: TIMER2 CONTROL REGISTER
U-0
—
bit 7
R/W-0
R/W-0
R/W-0
R/W-0
T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0
R/W-0
TMR2ON
R/W-0
T2CKPS1
R/W-0
T2CKPS0
bit 0
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
x = Bit is unknown
bit 7
bit 6-3
bit 2
bit 1-0
Unimplemented: Read as ‘0’
T2OUTPS<3:0>: Timer2 Output Postscale Select bits
0000 = 1:1 Postscale
0001 = 1:2 Postscale
•
•
•
1111 = 1:16 Postscale
TMR2ON: Timer2 On bit
1 = Timer2 is on
0 = Timer2 is off
T2CKPS<1:0>: Timer2 Clock Prescale Select bits
00 = Prescaler is 1
01 = Prescaler is 4
1x = Prescaler is 16
 2010-2012 Microchip Technology Inc.
DS39977F-page 221