Re: Re[2]: CIA and (fast) Serial Transfer.

From: David Wood (
Date: 2002-10-02 23:44:09

On Wed, 2 Oct 2002, groepaz wrote:

> mmmh... long ago i did the same and i _think_ getting rid of the
> unstableness was as easy as adding a pullup-resistor. (i dont think i used
> any inverters or sth that is)

I was going to recommend this on the first posting, but thought I'd read
through the whole thread first. :)

coax ethernet is terminated to 50 ohms on each end (25 ohms overall) with
one resistor across the line.  SCSI is terminated to about 130 ohms, I cant
remember the exact value, buy pulling 220 ohms against +5 and 330 against
ground on each end of the line.

You may want to try one or both of these termination schemes.  The first
gives a nice 10mhz lowvoltage signalling rate, and the second, with good
cabling, can give a 40mhz signalling rate using high-current drivers.

The actual values of the resistors used for termination here shouldnt be
used as a concrete value when choosing your termination, as they're
optimised for circuits other than the CIA sp's.  Make sure you terminate
both data -and- clock also.


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