DS 1307 Real time Clock interface with Intel 386EX processor

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Is it possible to hook pins SCL,SDA of Dallas DS1307 RTC with I/O
ports of Intel 386EX processor?

Thanks
learner

Re: DS 1307 Real time Clock interface with Intel 386EX processor
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I don't think there's any hardware reason why you couldn't do that and drive
the I2C protocol via pure software. I assume you mean regular digital I/O pins
and not to anything like a UART.

Re: DS 1307 Real time Clock interface with Intel 386EX processor
snipped-for-privacy@aol.com (Gary Kato) wrote in message
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I am using parallel I/O ports available in the processor. Do I need
pullup resistors to hook SCl and SDA to processor? I am new to this
field and any help will be appreciated.

Thanks

Re: DS 1307 Real time Clock interface with Intel 386EX processor
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What might be a problem is the open-drain nature (wire-and) of the
I2C bus. On many I/O ports, you'll need three-state buffers and
send the data via the output enable pin to simulate an open-drain
device.

If the output bits are easily individually controlled as inputs
or outputs, the same effect can be created using the data direction
register as the outputs and pre-set the output register bits to zeroes.

You have to create the bus sequences bit by bit in software.

HTH

Tauno Voipio
tauno voipio @ iki fi


Re: DS 1307 Real time Clock interface with Intel 386EX processor
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I'm not a hardware guy but it looks like you do need pullup resistors on both
lines. You might try getting a book like "Designing Embedded Hardware".

Re: DS 1307 Real time Clock interface with Intel 386EX processor
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SCL and SDA lines do need pullups, stick a 4K7 up to the positive supply
on each one. Even if the processor already has pullups it won't do any
harm
--
Tim Mitchell

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