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From: Ed McGettigan on 19 Jul 2010 12:26
On Jul 18, 10:37 pm, Muzaffer Kal <k...(a)dspia.com> wrote:
> On Sun, 18 Jul 2010 21:11:18 -0700 (PDT), Vips
>
> <thevipulsi...(a)gmail.com> wrote:
> >Thanks for the reply.. Let me add that the Master has SDA_IN( input)
> >SDA_TRISTATE( output) this is a simple output with no tristate. SCL_IN
> >(input) SCL_TRISTATE(OUTPUT). Now I am confused as How the first start
> >will be generated as who will toggle the SDA_IN line which is the
> >input to the master for the START generation while the SCK_IN is
> >high ....
>
> Because I2C is an open-drain (open collector) interface it doesn't
> need to drive any of the outputs high ie high level generation is done
> by the external pullup. This can be accomplished with a push-pull IO
> by driving a strong zero and tri-state for one. So you need a regular
> tri-state IO and drive zero when tri-state is inactive and tri-state
> when it is active ie (assuming active high tri-state IOPAD):
>
> IOPAD master_sda(.IN(sda_in), .OUT(sda_tristate), .OE(sda_tristate),
> .PAD(sda_wire));
> --
> Muzaffer Kal
>
> DSPIA INC.
> ASIC/FPGA Design Services
>
> http://www.dspia.com

Without knowing the functionality of the SDA_TRISTATE output (does
1=HiZ or does 1=Drive, my bet would be HiZ) and the functionality of
the IOPAD OE pin (this isn't a Xilinx cell, but OE usually mean Output
Enable/Drive) your code may not work.
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