PIC16F7X Datasheet, PDF (52/174 Pages) Microchip Technology – 28/40-Pin 8-Bit CMOS FLASH Microcontrollers

PIC16F7X
6.5 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 use with a 32 kHz crystal. Table 6-1 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.
6.6 Resetting Timer1 using a CCP
Trigger Output
If the CCP1 or CCP2 module is configured in Compare
mode to generate a “special event trigger”
(CCP1M3:CCP1M0 = ‘1011’), this signal will reset
Timer1.
Note:
The special event triggers from the CCP1
and CCP2 modules will not set interrupt
flag bit TMR1IF (PIR1<0>).
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 or CCP2, the write will
take precedence.
In this mode of operation, the CCPRxH:CCPRxL regis-
ter pair effectively becomes the period register for
Timer1.
6.7 Resetting of Timer1 Register Pair
(TMR1H, TMR1L)
TMR1H and TMR1L registers are not reset to 00h on a
POR, or any other RESET, except by the CCP1 and
CCP2 special event triggers.
TABLE 6-1: CAPACITOR SELECTION FOR
THE TIMER1 OSCILLATOR
Osc Type Frequency
Capacitors Used:
OSC1
OSC2
LP
32 kHz
47 pF
47 pF
100 kHz
33 pF
33 pF
200 kHz
15 pF
15 pF
Capacitor values are for design guidance only.
These capacitors were tested with the crystals listed
below for basic start-up and operation. These values
were not optimized.
Different capacitor values may be required to produce
acceptable oscillator operation. The user should test
the performance of the oscillator over the expected
VDD and temperature range for the application.
See the notes (below) table for additional information.
Commonly Used Crystals:
32.768 kHz
Epson C-001R32.768K-A
100 kHz
Epson C-2 100.00 KC-P
200 kHz
STD XTL 200.000 kHz
Note 1: Higher capacitance increases the stability
of the 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 appro-
priate values of external components.
T1CON register is reset to 00h on a Power-on Reset or
a Brown-out Reset, which shuts off the timer and
leaves a 1:1 prescale. In all other RESETS, the register
is unaffected.
6.8 Timer1 Prescaler
The prescaler counter is cleared on writes to the
TMR1H or TMR1L registers.
TABLE 6-2: REGISTERS ASSOCIATED WITH TIMER1 AS A TIMER/COUNTER
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, INTCON GIE
10Bh,18Bh
0Ch
PIR1
PSPIF⁽¹⁾
8Ch
PIE1
PSPIE⁽¹⁾
PEIE
ADIF
ADIE
TMR0IE
RCIF
RCIE
INTE
TXIF
TXIE
RBIE TMR0IF INTF RBIF 0000 000x 0000 000u
SSPIF CCP1IF TMR2IF TMR1IF 0000 0000 0000 0000
SSPIE CCP1IE TMR2IE TMR1IE 0000 0000 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: x = unknown, u = unchanged, - = unimplemented, read as '0'. Shaded cells are not used by the Timer1 module.
Note 1: Bits PSPIE and PSPIF are reserved on the PIC16F73/76; always maintain these bits clear.
DS30325B-page 50
 2002 Microchip Technology Inc.