try:-

Max127/8

http://209.1.238.250/arpdf/1890.pdf

Steve Lawther

> -----Original Message-----
> From: John Lawton Electronics [SMTP:mail@JLE.CO.UK]
> Sent: Monday, October 11, 1999 2:24 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Microwire/SPI connection lengths?
>
> I'm designing a controller, and for analog and digital I/O I want to use
> serial I/F devices with some devices remote from the micro board in
> several
> expansion boxes. I can't decide whether to use I2C or SPI/Microwire bus
> systems. Ideally I wouldn't use both.
>
> Each expansion box needs 4 or 8 latched outputs and 4 or 8 analog
> (12bit) inputs. (I haven't yet decided exact no of channels required per
> box).
>
> I don't really want to implement both buses, and would be happy with the
> I2C bus which is very simple, hardware wise, but I can't seem to get all
> the  chips in I2C with the functions I need.
>
> I thought to use I2C PCF8574's for each set of 4/8x latched outputs, but
> would
> then have to use SPI devices for each set of 4/8 I/P multiplexed 12 bit
> A/D,
> since I can't find a multichannel 12bit I2C A/D converter. I am
> considering
> the LTC1298 with LTC1390 multiplexer or an LTC1290.
> I don't need fast conversions. Any other suggestions?
>
> (Interestingly the LTC1380 is an SMB/I2C bus 8 I/P MPX chip, but Linear
> don't seem to do a matching 12 bit A/D converter with SMB/I2C bus. Does
> anyone do one?)
>
> Lastly, does anyone know what length of cables can I run between the micro
> and each expansion box, and/or any information on max capacitance loading
> /
> impedance levels for the two bus systems - I can't find this application
> information anywhere in the datasheets?
>
> Any help would be appreciated.
>
> John
>
> =========================================================
>  John Lawton Electronics: john@jle.co.uk   www.jle.co.uk
> =========================================================
>
>
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