PIC16LC773-04SLASHSP datasheet(43/200 Pages) MICROCHIP

43 / 200 page

PIC16C77X

Advance Information

DS30275A-page 43

5.2

Timer1 Oscillator

A crystal oscillator circuit is built in between pins T1OSI

(input) and T1OSO (amplifier output). It is enabled by

setting control bit T1OSCEN (T1CON<3>). The oscilla-

tor is a low power oscillator rated up to 200 kHz. It will

continue to run during SLEEP. It is primarily intended

for a 32 kHz crystal. Table 5-1 shows the capacitor

selection for the Timer1 oscillator.

The Timer1 oscillator is identical to the LP oscillator.

The user must provide a software time delay to ensure

proper oscillator start-up.

TABLE 5-1

CAPACITOR SELECTION FOR

THE TIMER1 OSCILLATOR

5.3

Timer1 Interrupt

The TMR1 Register pair (TMR1H:TMR1L) increments

from 0000h to FFFFh and rolls over to 0000h. The

TMR1 Interrupt, if enabled, is generated on overflow

which is latched in interrupt flag bit TMR1IF (PIR1<0>).

This interrupt can be enabled/disabled by setting/clear-

ing TMR1 interrupt enable bit TMR1IE (PIE1<0>).

5.4

Resetting Timer1 using a CCP Trigger

Output

If the CCP module is configured in compare mode to

generate a “special event trigger" (CCP1M3:CCP1M0

= 1011), this signal will reset Timer1 and start an A/D

conversion (if the A/D module is enabled).

Timer1 must be configured for either timer or synchro-

nized counter mode to take advantage of this feature. If

Timer1 is running in asynchronous counter mode, this

reset operation may not work.

In the event that a write to Timer1 coincides with a spe-

cial event trigger from CCP1, the write will take prece-

dence.

In this mode of operation, the CCPR1H:CCPR1L regis-

ters pair effectively becomes the period register for

Timer1.

TABLE 5-2

REGISTERS ASSOCIATED WITH TIMER1 AS A TIMER/COUNTER

Osc Type

Freq

32 kHz

33 pF

100 kHz

15 pF

200 kHz

15 pF

These values are for design guidance only.

Crystals Tested:

32.768 kHz

Epson C-001R32.768K-A

± 20 PPM

100 kHz

Epson C-2 100.00 KC-P

± 20 PPM

200 kHz

STD XTL 200.000 kHz

± 20 PPM

Note 1: Higher capacitance increases the stability

of oscillator but also increases the start-up

time.

2: Since each resonator/crystal has its own

characteristics, the user should consult the

resonator/crystal manufacturer for appropri-

ate values of external components.

Note:

The special event triggers from the CCP1

module will not set interrupt flag bit

TMR1IF (PIR1<0>).

Address

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Value on:

POR,

BOR

Value on

all other

resets

0Bh,8Bh,

10Bh,18Bh

INTCON

GIE

PEIE

T0IE

INTE

RBIE

T0IF

INTF

RBIF

0000 000x

0000 000u

0Ch

PIR1

PSPIF(1)

ADIF

RCIF

TXIF

SSPIF

CCP1IF

TMR2IF

TMR1IF

0000 0000

8Ch

PIE1

PSPIE(1)

ADIE

RCIE

TXIE

SSPIE

CCP1IE

TMR2IE

TMR1IE

0000 0000

0Eh

TMR1L

Holding register for the Least Significant Byte of the 16-bit TMR1 register

xxxx xxxx

uuuu uuuu

0Fh

TMR1H

Holding register for the Most Significant Byte of the 16-bit TMR1 register

xxxx xxxx

uuuu uuuu

10h

T1CON

—

T1CKPS1

T1CKPS0

T1OSCEN

T1SYNC

TMR1CS

TMR1ON

--00 0000

--uu uuuu

Legend:

= unknown, u = unchanged, - = unimplemented read as '0'. Shaded cells are not used by the Timer1 module.

Note

These bits are reserved on the 28-pin devices, always maintain these bits clear.

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