PIC16C745SLASHP datasheet(49/158 Pages) MICROCHIP

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Advanced Information

DS41124A-page 49

PIC16C745/765

8.0

TIMER2 MODULE

Timer2 is an 8-bit timer with a prescaler and a

postscaler. It can be used as the PWM time-base for

the PWM mode of the CCP module(s). The TMR2 reg-

ister is readable and writable, and is cleared on any

device reset.

The input clock (FINT/4) has a prescale option of 1:1,

1:4 or 1:16, selected by control bits T2CKPS<1:0>

(T2CON<1:0>).

The Timer2 module has an 8-bit period register PR2.

Timer2 increments from 00h until it matches PR2 and

then resets to 00h on the next increment cycle. PR2 is

a readable and writable register. The PR2 register is ini-

tialized to FFh upon reset.

The match output 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>)).

Timer2 can be shut off by clearing control bit TMR2ON

(T2CON<2>) to minimize power consumption.

Additional information on timer modules is available in

the PICmicro™ Mid-Range MCU Family Reference

Manual (DS33023).

8.1

Timer2 Prescaler and Postscaler

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 (POR, MCLR reset, WDT reset

or BOR)

TMR2 is not cleared when T2CON is written.

8.2

Output of TMR2

The output of TMR2 (before the postscaler) is fed to the

SSPort module, which optionally uses it to generate

shift clock.

FIGURE 8-1:

TIMER2 BLOCK DIAGRAM

TIMER2 CONTROL REGISTER (T2CON: 12h)

Comparator

TMR2

Sets flag

TMR2 reg

output (1)

Reset

Postscaler

Prescaler

PR2 reg

FINT

1:1

1:16

1:1, 1:4, 1:16

bit TMR2IF

Note 1:

TMR2 register output can be software selected by the

SSP module as a baud clock.

T2OUTPS<3:0>

T2CKPS<1:0>

U-0

R/W-0

—

TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0

TMR2ON

T2CKPS1 T2CKPS0

= Readable bit

W = Writable bit

= Unimplemented bit,

read as ‘0’

- n = Value at POR reset

bit7

bit0

bit 7:

Unimplemented: Read as '0'

bit 6-3:

TOUTPS<3:0>: Timer2 Output Postscale Select bits

0000

= 1:1 Postscale

0001

= 1:2 Postscale

0010

= 1:3 Postscale

•

1111

= 1:16 Postscale

bit 2:

TMR2ON: Timer2 On bit

= Timer2 is on

= Timer2 is off

bit 1-0:

T2CKPS<1:0>: Timer2 Clock Prescale Select bits

= Prescaler is 1

= Prescaler is 4

= Prescaler is 16

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