The I2C standard uses the least significant bit of the slave address (i.e.
A0) as a flag to tell the slave device whether you want to read or write.
It was a simple way to implement the read write bit, but had the side effect
of reducing the maximum number of possible slave addresses to 127.

Cheers

Mike Rigby-Jones

> -----Original Message-----
> From: Goovaerts [SMTP:goofy1@GLO.BE]
> Sent: Wednesday, August 18, 1999 6:24 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      NVM's, I'm a little bit in the dark here !
>
> Can anyone help me on my way with NVM's ?? I have to read out the two
> pages
> of an NVM --> X24C04 . This particular NVM has only two pages of 256
> bytes,
> each with its own slave address. These slave addresses for the pages are :
>
>         A0 and A2 --> Why do they differ by two ??
>
> I know it has something to do with reading and writing these NVM pages.
>
> When you want to write to the first page, you write to adres A0.
> But, when you want to read from the first page, you have to read from
> adres
> A1.
>
> I really don't get this.
>
> Anyone ??
>
> Glenn Goovaerts