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From: Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>
To: David Brownell <david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>
Cc: jack.ren-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org,
	linux-arm-kernel-xIg/pKzrS19vn6HldHNs0ANdhmdF6hFW@public.gmane.org,
	i2c-GZX6beZjE8VD60Wz+7aTrA@public.gmane.org
Subject: Re: [PATCH] gpio: max732x: add support for MAX7319, MAX7320-7327 I2C   Port Expanders
Date: Sun, 13 Jul 2008 11:18:47 +0200	[thread overview]
Message-ID: <20080713111847.69b35ce5@hyperion.delvare> (raw)
In-Reply-To: <20080713091236.015E920ABDD-ZcXrCSuhvln6VZ3dlLfH/g4gEjPzgfUyLrfjE7I9kuVHxeISYlDBzl6hYfS7NtTn@public.gmane.org>

On Sun, 13 Jul 2008 02:12:36 -0700, David Brownell wrote:
> > 3. for chips like max732x, actually, the range of 0x50 - 0x5F will be
> > monitored by the I2C chips at startup to decide the connections of
> > AD2/AD0 pins to GND/VCC/SCL/SDA,
> 
> There's no need to monitor addresses ... before the first data bit
> is sent -- whatever value! -- it's known how those pins are wired:
> 
>  - START bit ... SCL is high, SDA falls.  Any pin that stayed
>    low is wired to ground.  Any pin that changed high-to-low is
>    thus connected to SDA.
> 
>  - Prepare to send first bit ... SDA still low, SCL falls.  Any
>    pin that stayed high is wired to Vcc.  Any pin that changed
>    high-to-low is connected to SCL.
> 
> And then the master updates SDA to match the first (address) bit,
> and lets SCL be pulled high ... the i2c slave has all the data it
> needs to be able to determine its address.

Totally true. Add to this that the first 3 address bits can't change,
this gives the chip some more time to setup its internal logic to match
the 4 LSBs by the time they come.

-- 
Jean Delvare

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i2c mailing list
i2c-GZX6beZjE8VD60Wz+7aTrA@public.gmane.org
http://lists.lm-sensors.org/mailman/listinfo/i2c

  parent reply	other threads:[~2008-07-13  9:18 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-07-10  6:13 [PATCH] gpio: max732x: add support for MAX7319, MAX7320-7327 I2C Port Expanders Eric Miao
     [not found] ` <4875A893.3090402-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2008-07-11  8:29   ` Jean Delvare
     [not found]     ` <20080711102952.31d2d943-ig7AzVSIIG7kN2dkZ6Wm7A@public.gmane.org>
2008-07-11  8:57       ` eric miao
     [not found]         ` <f17812d70807110157p5e421222sc9ef420ceb80970c-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2008-07-11  9:31           ` Jean Delvare
     [not found]             ` <20080711113114.79d80212-ig7AzVSIIG7kN2dkZ6Wm7A@public.gmane.org>
2008-07-11  9:39               ` eric miao
     [not found]                 ` <f17812d70807110239q6c175f5cn70db966681ae387d-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2008-07-11  9:48                   ` eric miao
     [not found]                     ` <f17812d70807110248y7fab3328q59ea41084c491df-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2008-07-11 11:15                       ` Jean Delvare
2008-07-11 21:25                       ` David Brownell
     [not found]                         ` <200807111425.00961.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>
2008-07-12  7:16                           ` Jean Delvare
     [not found]                             ` <20080712091610.4ec242c3-ig7AzVSIIG7kN2dkZ6Wm7A@public.gmane.org>
2008-07-12  7:46                               ` David Brownell
     [not found]                                 ` <200807120046.29389.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>
2008-07-12  7:53                                   ` Jean Delvare
     [not found]                                     ` <20080712095300.1ba4b3a7-ig7AzVSIIG7kN2dkZ6Wm7A@public.gmane.org>
2008-07-12 21:42                                       ` David Brownell
2008-07-13  6:55                                         ` Jean Delvare
2008-07-13  6:04                                   ` eric miao
     [not found]                                     ` <f17812d70807122304o533d8af9k1384db653b264912-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2008-07-13  7:20                                       ` Jean Delvare
     [not found]                                         ` <20080713092050.6dffd8d3-ig7AzVSIIG7kN2dkZ6Wm7A@public.gmane.org>
2008-07-13  8:53                                           ` eric miao
     [not found]                                             ` <f17812d70807130153g290e17ecq10ab12529effc8d4-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2008-07-13  9:13                                               ` Jean Delvare
     [not found]                                                 ` <20080713111306.791bbc41-ig7AzVSIIG7kN2dkZ6Wm7A@public.gmane.org>
2008-07-13 13:45                                                   ` eric miao
     [not found]                                                     ` <f17812d70807130645i755c1c62la30d5c515c2d2080-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2008-07-13 19:18                                                       ` David Brownell
     [not found]                                                         ` <200807131218.29575.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>
2008-07-14  1:35                                                           ` Eric Miao
2008-07-13  9:12                                           ` David Brownell
     [not found]                                             ` <20080713091236.015E920ABDD-ZcXrCSuhvln6VZ3dlLfH/g4gEjPzgfUyLrfjE7I9kuVHxeISYlDBzl6hYfS7NtTn@public.gmane.org>
2008-07-13  9:18                                               ` Jean Delvare [this message]
2008-07-13 14:37                                       ` Jean Delvare
2008-07-11  9:54                   ` Jean Delvare
     [not found]                     ` <20080711115436.22134ce7-ig7AzVSIIG7kN2dkZ6Wm7A@public.gmane.org>
2008-07-11 10:04                       ` eric miao

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