SPI unterminated

From: Dave Boland (NODARNSPAMdboland9_at_stny.rr.com)
Date: 03/03/05 

Date: Thu, 03 Mar 2005 15:47:35 GMT

I saw some postings about cards that have an SPI interface,
which made me think about a few things relative to a project
I'm doing. In this case, the plan is to run the SPI signal
lines and three chip selects to some header pins. Up to
three daughter cards can be stacked on the processor card,
and some or all may have SPI devices.

My concerns are for unterminated SPI lines and radiated EMI.
  Initial calculations look like reflections from an
umterminated line shouldn't be a problem because a 12.5 MHz
signal has a wave length of about 79 feet, which is much
longer than trace lengths for the SPI bus. This ignores the
effects of the rise time of the waveform though.

I haven't attempted to deal with EMI at this stage of
development, but it is always a concern. This is especially
true when a clock is passed from card to card and there will
be a pin radiating the clock (top card on the stack).

Has anyone done a design similar to this and got it through
UL/CSA/IEC? If so, I would appreciate any helpful advice.

Thanks,
Dave

Relevant Pages

  • Re: [PATCH] 4/5: Updates to SPI and mmc_spi: mmc_spi updated, kernel 2.6.19
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  • Re: SPI unterminated
    ... Dave Boland wrote: ... the plan is to run the SPI signal lines and three chip selects to ... > processor card, and some or all may have SPI devices. ... This is especially true when a clock is passed ...
    (sci.electronics.design)
  • Re: SPI unterminated
    ... the plan is to run the SPI signal lines and three chip selects to ... > processor card, and some or all may have SPI devices. ... > My concerns are for unterminated SPI lines and radiated EMI. ... This is especially true when a clock is passed ...
    (sci.electronics.design)
  • Re: [RFC][PATCH] SPI subsystem
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