PIC12F629 with crystal oscillator

[Fero]

Hi,
i have a circuit with 2 PIC12F629 with crystal oscillator 4 MHz. I
have currently 2 crystal 4 MHz ( one PIC12F629 - one crystal 4 MHz ).
It is possible using 1 crystal 4 MHz for both PIC 12F629 ?

Thanks.

Fero

 

[Roger Hamlett]

Hi,
i have a circuit with 2 PIC12F629 with crystal oscillator 4 MHz. I
have currently 2 crystal 4 MHz ( one PIC12F629 - one crystal 4 MHz ).
It is possible using 1 crystal 4 MHz for both PIC 12F629 ?

Do you have a crystal, using the PIC's own oscillator, or a 'crystal
oscillator' module?. If the latter, then the answer is 'yes'. Most of
these have a 'fanout' of perhaps 4 or more, and will drive two PIC's
inputs without problems. If the former, then the answer is less certain. I
can be made to work (you program the second PIC into EC mode, and connect
it's CKIN pin to the CKOUT of the first chip). However the extra load, and
capacitance, may require you to adjust the drive to the crystal, and may
cause the frequency to shift slightly. Look at the Microchip application
note 'AN949', and the note near the end of this.

Best Wishes

 

[Tim Wescott]

Do you have a crystal, using the PIC's own oscillator, or a 'crystal
oscillator' module?. If the latter, then the answer is 'yes'. Most of
these have a 'fanout' of perhaps 4 or more, and will drive two PIC's
inputs without problems. If the former, then the answer is less certain. I
can be made to work (you program the second PIC into EC mode, and connect
it's CKIN pin to the CKOUT of the first chip). However the extra load, and
capacitance, may require you to adjust the drive to the crystal, and may
cause the frequency to shift slightly. Look at the Microchip application
note 'AN949', and the note near the end of this.

Best Wishes

A tiny logic 74HCU04 would put that to rights.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

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