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I2C, SPI & Microwire

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Tom Rodger

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Mar 26, 1997, 3:00:00 AM3/26/97
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Hi,

I wonder if anybody could help me?
I am looking for information on the 3 types of
bus interfaces - I2C, SPI & Microwire.

I have searched through the Philips &
National Semiconductor homepages but they
are too application specific.

I really need more general information on the differences
between the three so that I can draw up a
comparative report.

If anybody has any information or can point me in the
right direction, then please let me know.

Cheers
Tom


M Simon

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Mar 27, 1997, 3:00:00 AM3/27/97
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First draw up a criteria list:

Speed, #units on a bus, maximum distance, etc.

Once you know what you are looking for its easy to find.

Simon
---------------------------------------------------


Tom.R...@dial.pipex.com (Tom Rodger) wrote:


>Hi,

>Cheers
>Tom


In the end people get the government they deserve.

Read "The Weapon Shops of Isher" by A.E. vanVogt

Simon


Marc 'Nepomuk' Heuler

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Mar 28, 1997, 3:00:00 AM3/28/97
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In article <333A1B...@mindspring.com>, John Wettroth writes:

> I2C- is truly a 2 wire multidrop bus that runs at 100KHz or 400Khz for
> newer devices (fast-I2C).

Are there 400KHz SO-8 EEPROMs already?

> SPI and Microwire: These are almost identical. Microwire chip selects
> are generally active high while SPI are active low. There's a fancier
> SPI called QSPI supported by Motorola processors with a lot of queuing
> hardware built in so the software doesn't have to work so hard. This is
> a 4 plus wire bus but can be operated on 3 and even 2 in crude
> applications.

I checked the ST93C46 datasheet (a microwire bus EEPROM) and can't imagine
how to operate it on 2 wires. For "Write", it sais, I have to clock (1st
wire) data (2nd wire) into the chip, then deselect (3rd wire) it to start
the programming cycle. So even when I short D (data in) and Q (data out),
I still need 3 wires. Am I missing something?

John Wettroth

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Mar 31, 1997, 3:00:00 AM3/31/97
to ma...@aargh.franken.de

Marc 'Nepomuk' Heuler wrote:

> I checked the ST93C46 datasheet (a microwire bus EEPROM) and can't imagine
> how to operate it on 2 wires. For "Write", it sais, I have to clock (1st
> wire) data (2nd wire) into the chip, then deselect (3rd wire) it to start
> the programming cycle. So even when I short D (data in) and Q (data out),
> I still need 3 wires. Am I missing something?

In crude applications refers to output only applications like a display
driver.
In an eeprom, you'll need at least 3 wires- you've missed nothing.

Regards,
John Wettroth

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