What bus termination is needed for main CPU clock of 40Mhz?

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ze_dib

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Data bus Terminaison

Hi guys,

I'm designing a board with MPC555 in extended mode. I'd like to know what bus terminaisons (if mandatory) are needed for a Main CPU clock of 40 MHz.

Regards,

Ze_DIB
 

Re: Data bus Terminaison

Hi,
At 40MHz you do not need any terminations. Do check if requires to be tied up or low for some reason. Normally it would be recommeded to tie high the unused pins. (i dont know if it is general)
B R M
 

Re: Data bus Terminaison

In my view, the most important is the clock topology. And the source resistance is also necessary. It seems that the end terminal resistor might not very useful.
 

Data bus Terminaison

As i know , PCI bus (33Mhz) do not need terminations.
 

Re: Data bus Terminaison

No, I don’t think you need any termination

The need of termination depends on the rise/fall time of the signal and the wire length.

If you want to learn more about it, read High-Speed Digital Design,
A Handbook of Black Magic by Howard W. Johnson, www.sigcon.com
 

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