MPC5xxxのトピックAbout spc5777c external oscillator configuration

About spc5777c external oscillator configuration

liuxingqiao — Wed, 30 Aug 2017 10:49:29 GMT

Hello,

According to the reference manual, the on chip crystal oscillator can be bypassed to source a clock directly from the EXTAL pin(bypass mode), and the bypass configuration is controlled by bit 24 of the Miscellaneous DCF record. I want to use an external oscillator to provide clock signal to EXTAL pin, and I have two questions:

1. Should the XTAL pin be left unconnected, or be grounded?

2. If bit 24 of the Miscellaneous DCF record is set to '1'(Oscillator enabled), would the external oscillator be influnced by internal oscillator circuits? Would the external oscillator or internal oscillator circuits be damaged?

Thanks.

Re: About spc5777c external oscillator configuration

davidtosenovjan — Wed, 30 Aug 2017 12:39:26 GMT

1) Leave XTAL pin floating.

2) No, it should not cause any damage. Disabling of internal oscillator in DCF client probably will lead in slightly decreased overall device power consumption.

Re: About spc5777c external oscillator configuration

liuxingqiao — Wed, 30 Aug 2017 14:52:43 GMT

Thanks for your answer.

Best Regards,

liu xingqiao