PIC18FXX20
13.0
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TIMER2 MODULE
13.1
Timer2 Operation
The Timer2 module timer has the following features:
8-bit timer (TMR2 register)
8-bit period register (PR2)
Readable and writable (both registers)
Software programmable prescaler (1:1, 1:4, 1:16)
Software programmable postscaler (1:1 to 1:16)
Interrupt on TMR2 match of PR2
SSP module optional use of TMR2 output to
generate clock shift
Timer2 can be used as the PWM time-base for the
PWM mode of the CCP module. The TMR2 register is
readable and writable, and is cleared on any device
RESET. The input clock (F
OSC
/4) has a prescale option
of 1:1, 1:4 or 1:16, selected by control bits,
T2CKPS1:T2CKPS0 (T2CON<1:0>). The match out-
put of TMR2 goes through a 4-bit postscaler (which
gives a 1:1 to 1:16 scaling inclusive) to generate a
TMR2 interrupt (latched in flag bit, TMR2IF (PIR1<1>)).
The prescaler and postscaler counters are cleared
when any of the following occurs:
• 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.
Timer2 has a control register shown in Register 13-1.
Timer2 can be shut-off by clearing control bit, TMR2ON
(T2CON<2>), to minimize power consumption.
module. Register 13-1 shows the Timer2 control regis-
ter. The prescaler and postscaler selection of Timer2
are controlled by this register.
REGISTER 13-1:
T2CON: TIMER2 CONTROL REGISTER
U-0
—
bit 7
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
bit 0
T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0
bit 7
bit 6-3
Unimplemented:
Read as '0'
T2OUTPS3:T2OUTPS0:
Timer2 Output Postscale Select bits
0000
= 1:1 Postscale
0001
= 1:2 Postscale
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1111
= 1:16 Postscale
TMR2ON:
Timer2 On bit
1
= Timer2 is on
0
= Timer2 is off
T2CKPS1:T2CKPS0:
Timer2 Clock Prescale Select bits
00
= Prescaler is 1
01
= Prescaler is 4
1x
= Prescaler is 16
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 2
bit 1-0
2003 Microchip Technology Inc.
Advance Information
DS39609A-page 141
MICROCHIP [ MICROCHIP TECHNOLOGY ]
