Re: Exorcisor Schematic Error

On Mon, 22 Dec 1997, fishd wrote:

> The ENT / ENP error was a carry over. Whoever generated that library
> at work screwed up, I never noticed it. Like Joe said it makes no
> difference when wiring up to pins of real parts. Another thing
> you will definitely want to look into is the CLOCK input. The
> original design is marginal at best and has been giving me no end
> of trouble. My Exorcisor works fine on some boards and not at all
> on another. Removing the capacitors on the CLK input is a must and
> getting rid of the 100 Ohm current limit resistor also should be
> done. A 2K pull-up resistor at the input helped get the levels
> to where they should be but I'm still going to have to improve
> the ground connections. I'm getting too much ringing on the CLK
> input which is probably what's causing the marginal condition.
> I just wish that I had more time to play with it to get it right.

        Now that you mention the ringing problem, I'm sure that's
why there was that obscene amount of capacitance and the resistor
there -- to terminate the transmission line on the CLK line.

        Inductance on the GND and VCC lines probably isn't helping
(Because VCC is bouncing down and GND is bouncing up.) What are you
using to connect the exorcisor to the board?

        I'll come up with a good way to terminate all those
connections, since I'll have the same problem you are....

Joe
 
Received on Mon Dec 22 15:23:11 1997