18F8680 datasheet(164/496 Pages) MICROCHIP

164 / 496 page

PIC18F6585/8585/6680/8680

DS30491C-page 162

 2004 Microchip Technology Inc.

13.0

TIMER2 MODULE

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 has a control register shown in Register 13-1.

Timer2 can be shut-off by clearing control bit, TMR2ON

(T2CON<2>),

minimize

power

consumption.

Figure 13-1 is a simplified block diagram of the Timer2

module. Register 13-1 shows the Timer2 Control regis-

ter. The prescaler and postscaler selection of Timer2

are controlled by this register.

13.1

Timer2 Operation

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 (FOSC/4) has a prescale option

of 1:1, 1:4 or 1:16, selected

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.

T2CON: TIMER2 CONTROL REGISTER

U-0

R/W-0

—

T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0

bit 7

bit 0

bit 7

Unimplemented: Read as ‘0’

bit 6-3

T2OUTPS3:T2OUTPS0: Timer2 Output Postscale Select bits

0000

= 1:1 postscale

0001

= 1:2 postscale

•

1111

= 1:16 postscale

bit 2

TMR2ON: Timer2 On bit

= Timer2 is on

= Timer2 is off

bit 1-0

T2CKPS1:T2CKPS0: Timer2 Clock Prescale Select bits

= Prescaler is 1

= Prescaler is 4

= Prescaler is 16

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

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