trantow@csd4.milw.wisc.edu (Jerry J Trantow) (05/11/89)
Line Eater fodder Well, my wife has finished her paper and it is finally safe for me to reinstall the LUCAS board. I had my board working for a few months when it decided to get flakey after warming up. Now I am ready to try again. I decided to add the legendary bus termination fix and I have come up with a few questions. The fix that has been suggested uses a 1K,4.7K, and 0.001 uF. Someone also suggested using a 3.3K instead of the 4.7K, and a variable pot was also mentioned. To clear up the confusion, I dug up my A1000 schematics. The expansion board that is shown in the schematics shows a 220 and 330 ohm bus termination with no capacitor on the data/address lines and a capacitor on the Clock lines. So what is the scoop. Is the capacitor really needed? Should I put Rs on the address, data, and control lines? By the way, when I first looked at this I thought it would really be a pain. I had not realized that they make 10 pin SIPs that have the termination network (Rs) all set up.
daveh@cbmvax.UUCP (Dave Haynie) (05/12/89)
in article <2487@csd4.milw.wisc.edu>, trantow@csd4.milw.wisc.edu (Jerry J Trantow) says: > Summary: What's the Scoop > Line Eater fodder > The fix that has been suggested uses a 1K,4.7K, and 0.001 uF.... > To clear up the confusion, I dug up my A1000 schematics. The expansion board > that is shown in the schematics shows a 220 and 330 ohm bus termination ... > So what is the scoop. Is the capacitor really needed? Should I put Rs on > the address, data, and control lines? The resistive termination is appropriate for an expansion bus with good, strong bus drivers, like the 74F245s recommended for that Los Gatos backplane design. What you're talking about is sitting on the Amiga's local bus. I doubt that the local bus will be able to drive such termination. The R-C termination that's been suggested for LUCAS is probably best. Not only is it mild enough to let the rest of the system keep working, but there's a good chance that it's tuned to the particular interface problems that exist beween LUCAS and the A1000. If you know the exact situation you're trying to supply termination for, you can do an application specific job. If you're trying instead to terminate an "anything goes here" thing, like an expansion bus, you do things a little differently. -- Dave Haynie "The 32 Bit Guy" Commodore-Amiga "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: D-DAVE H BIX: hazy Amiga -- It's not just a job, it's an obsession