2010 Microchip Technology Inc.
Preliminary
DS41350E-page 111
PIC18F/LF1XK50
12.0
TIMER2 MODULE
The Timer2 module timer incorporates the following
features:
8-bit timer and period registers (TMR2 and PR2,
respectively)
Readable and writable (both registers)
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 12-1), which enables or disables the timer
and configures the prescaler and postscaler. Timer2
can be shut off by clearing control bit, TMR2ON of the
T2CON register, to minimize power consumption.
A simplified block diagram of the module is shown in
12.1
Timer2 Operation
In normal operation, TMR2 is incremented from 00h on
each clock (FOSC/4). A 4-bit counter/prescaler on the
clock
input
gives
direct
input,
divide-by-4
and
divide-by-16 prescale options; these are selected by
the prescaler control bits, T2CKPS<1:0> of the T2CON
register. The value of TMR2 is compared to that of the
period register, 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 12.2 “Timer2
The TMR2 and PR2 registers are both directly readable
and writable. The TMR2 register is cleared on any
device Reset, whereas the PR2 register initializes to
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, MCLR Reset,
Watchdog Timer Reset or Brown-out Reset)
TMR2 is not cleared when T2CON is written.
REGISTER 12-1:
T2CON: TIMER2 CONTROL REGISTER
U-0
R/W-0
T2OUTPS3
T2OUTPS2
T2OUTPS1
T2OUTPS0
TMR2ON
T2CKPS1
T2CKPS0
bit 7
bit 0
Legend:
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
x = Bit is unknown
bit 7
Unimplemented: Read as ‘0’
bit 6-3
T2OUTPS<3:0>: Timer2 Output Postscale Select bits
0000
= 1:1 Postscale
0001
= 1:2 Postscale
1111
= 1:16 Postscale
bit 2
TMR2ON: Timer2 On bit
1
= Timer2 is on
0
= Timer2 is off
bit 1-0
T2CKPS<1:0>: Timer2 Clock Prescale Select bits
00
= Prescaler is 1
01
= Prescaler is 4
1x
= Prescaler is 16
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