PIC18F242 datasheet(113/332 Pages) MICROCHIP

113 / 332 page

DS39564C-page 111

PIC18FXX2

12.0

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 12-1.

Timer2 can be shut-off by clearing control bit TMR2ON

(T2CON<2>)

minimize

power

consumption.

Figure 12-1 is a simplified block diagram of the Timer2

module. Register 12-1 shows the Timer2 control regis-

ter. The prescaler and postscaler selection of Timer2

are controlled by this register.

12.1

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

1:1,

1:4

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

—

TOUTPS3

TOUTPS2

TOUTPS1

TOUTPS0

TMR2ON T2CKPS1

T2CKPS0

bit 7

bit 0

bit 7

Unimplemented: Read as '0'

bit 6-3

TOUTPS3:TOUTPS0: 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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