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Message
From: tkafafi at hotmail.com<tkafafi@h...>
Date: Mon Oct 1 03:52:35 CEST 2007
Subject: [oc] i2c Slave Design Ideas
Hi Steve,
I recall the i2c specification requires filtering for the fast and highspeed
modes, but not necessarily for the standard mode (0 to 100KHz). But I
agree with you that for any real world application you need the filtering.
I was thinking more along the lines if this is a univeristy level project
intended for operation in a lab environement, then you can drop the
filtering requirement. Even in a commercial environement you may those
to imlement the filtering in the analog domain. Such an approach may
make sense if none of the pads in your library meet the drive
requirements and you need to develop a custom pad for I2C, you may
decide to through in the filtering in the pad too.
----- Original Message -----
From: Steve Wilson<stevew@k...>
To:
Date: Tue Sep 25 16:10:36 CEST 2007
Subject: [oc] i2c Slave Design Ideas
> tkafafi at hotmail.com Wrote:
> >If you do not think noise will be an issue in your environment
> you can
> >the SCL as a clock. However, for detecting start and stop
> consitions, I
> >recall that you need to use SDA as the clock and SCL as the
> data.
> Let me confirm this point. The I2C specification requires the
> rejection of up
> to 50ns duration glitches. So use of a digital delay line that
> requires
> multiple clocks worth of stability is a must to get I2C to work.
> Don't forget that you can be driving up to 400pf worth of load -
> and the bus
> is going to have significant reflections.
> That digital filter seems to be a requirement in any significant
> (large)
> applications - and least anything not point to point.
> Steve Wilson
>
>
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