Guillermo Hernan Acosta

ECLK or two crystals in the same PCB

Discussion created by Guillermo Hernan Acosta on Jun 4, 2008
Latest reply on Jun 6, 2008 by Guillermo Hernan Acosta
Hello everyone.

I have a project, using two MCU: MC9S12UF32 and MC9S08AW60. I need to make them work at full bus frequency: 30MHz and 20MHZ respectively.

I could use MC9S08 internal self-clocked source but I need high clock accuracy.

Can I use two oscillator crystals of 12MHz and 4 MHz in the same PCB without inducting noise?
Or I can use the ECLK signal, in expanded mode, to drive the 8-bit MCU? If I do so, could I use 9S12 ECLK at 30MHz or 20MHz, driving 9S08 MCU in EXTAL pin at 15MHz or 20MHz bus frequency respectively?
I want also to use external memory, at full speed (30MHz bus frequency) if I can.

What do you recomend?
Thank you.
Best regards,
Hernán Acosta